Let’s see if this works. The aim is to review some of the S1 options. This is focussed on S1 racing, so it’s cars tuned to S900. This main post will list the cars, with the cars being reviewed in individual posts below. These cars (generally) won’t be meta options but are cars that should be competitive and probably not used that often online.
Ferrari Enzo
The Enzo is one of the most beautiful cars ever made but it’s also a competitive option in Forza S1. Rexazr’s tune uses the very popular rally tyres for road racing. With 775bhp the Enzo has an average top speed for S1 of around 215mph but it’s cornering is very strong. Most high speed corners can be taken flat out, enabling you to power through street races particularly.
For AWD, this car can’t compete with the FXX and GT05 which are the best in class but its a good second tier option and very smooth to drive. It’s comparable to something like the R390, which I know is used by some forum members.
Custom adventure clip:
https://xboxclips.co/jezza14/8846b2eb-d001-4176-9f47-3df097bb3eaf
Rivals times:
Emerald - 44.288
Reservorio - 1.59.578
Gran Pantano - 2.07.077
These times are just one run, so not optimised, but intended to give rough comparisons for a circuit, technical sprint and high speed sprint.
KTM Xbow GT4
The Xbow GT4 is an exclusive car so, if you don’t already own one, you might need to shell out a few million at the AH. However, it’s one of the best handling cars in S1. Cast Haste’s tune is RWD but, save for a little bit of throttle control, it’s glued to the track. With a top speed on only around 160mph you don’t want to take this for a run on Goliath but for circuits and really technical sprints, it’s a fun option to demolish the more standard cars. Fortunately, open racing often has at least two circuits, so with careful use it can be fairly effective. Here’s a clip showing how quickly you can make up lost time through the corners:
https://xboxclips.co/jezza14/ddc39e36-7aaf-46f9-a884-0065f51aac65
Rivals times:
Emerald - 44.094
Reservorio - 2.01.246
Gran Pantano - 2.21.241
That X-BOW was RWD? Seemed very steady in the corners. I know a lot of that is the driver’s ability to apply proper throttle control too though. Very impressive.
For the X-Bow I would probably switch to AWD Racing V8.
Just a more PI-efficient build. Should achieve faster times nearly everywhere and has the launch advantage for online races.
Yeah, fair point. I like the RWD version as it is fun to drive but the AWD tune for the Xbow GT4 is stronger. BedlamBorealis’ tune does a fairly easy 1.58 at Reservorio and 2.15 at Gran Pantano.
Since the Bone Shaker thread got locked (thankfully) and I wanted to answer to your A800 list I thought I do it here since it’s a car thread anyway.
For A800 I would recommend following cars (neither of them is meta, just good & fun):
The new Z4
AWD Rallies M3 V8 swap Schnitzer kit. Extremely planted, good handling, good top end, mediocre acceleration. A car for speed carry.
Toyota MR2
RWD Race tires, centrifugal Civic swap & rear aero. Quite good on handling focussed tracks. Not much top end.
TVR Griffith
RWD detune on Drifts with the Diesel swap.
The strong base of the Griffith carries the weak engine. Definitely something else but more on the slower side.
Maserati Levante
AWD Rallies, centrifugal 458 engine.
Imho one of the best SUV. Good handling, strong engine. Brakes are awful and need time to adjust.
Ferrari F355
AWD, Rallies, centrifugal charged.
Probably the strongest car I use. Simply good.
Porsche 356
RWD, Slicks, WRX engine
My absolute favourite. Exceptional low speed acceleration. But I know you don’t like the engine and gearbox quirks of it.
If it’s the correct Ferrari I’ve just been trying this one to remove my one boneshaker time from a rivals board. It’s good enough to do it (I’m the weak link here) as one messed up corner cost me the time by 0.01.
I don’t think I have shared any of the above revisions.
Maybe some old ones that aren’t up to date with the latest tuning knowledge.
Cheers Rayne. Yeah, we can use this as a general car chat thread. I don’t think I have any of those ones tuned so I’ll try them. The two RS4s, F40, 99 Viper and 370Z were my main choices last night (plus powerbuild Cobra).
For dirt I like the TVR speed 12 in S1 class,not bad in cc too.
Lazydata tune i use most often,not fastest tune out there, but has good brakes so i prefer it for racing.I’ve won road races with the same tune too,but only after i picked it by mistake 
Sep4s tune (not sure of spelling,near top of s1 searches tho) is faster,but laughable brakes,prob better for Rivals.
Edit.I did get schooled in it by an Elise GT1 yesterday ,1s/lap slower in 2 circuit races,and 2secs over the trail,where i think he might have even been taking it easy
The No.25 Ferrari is another great S1900 car when tuned down.
I think the Lambo Gallardo Superlegerra is a nice S1 car. You get it for the Mogul accolade if I recall correctly. Not the fastest outright, but it’s very forgiving and precise. Lots of nice tunes available and without the ugly Forza aero. I am still deciding which one I like most but Only Naps tune (802 394 758) feels decent.
I also like the Focus RS 2017 (tune 177 881 040 - K17 Suimin) for S1 acceleration sprints. Competetive and budget friendly.
The Koenigsegg CC8S isn’t the easiest to handle but feels absolutely cracked for an S1 that drives somewhat predictably (tune 159 174 459 - Buntaaaaaa)
For A dirt a very strong BS alternative is the Maserati 8CTF (tune 940 392 357 - Rocklxd) - looks and sounds the buisness. 
Just some ones I’ve enjoyed using. Hopefully helps some others find more cars they like. 
Back to the original topic, and the third car I’ve reviewed:
Porsche 911 GT1 Strassenversion
Tune: Rexazr (176 307 450)
Drivetrain: RWD
Tyres: Stock
HP: 785hp
This is the overall strongest of the cars reviewed so far. It’s light weight (922kg) gives it excellent acceleration and control through fast corners. It’s top speed of around 215mph isn’t exceptional for RWD but you still won’t be losing too much ground to most cars you come across in S1 class. It’s the most difficult car to drive of the three reviewed so far, and you do have to be careful with the throttle at least until you have reached 4th gear, but once up to speed it’s extremely slick. This particular build is more balanced, making it strong in both sprints and circuits and it can cope with both relatively technical events and power courses (although I wouldn’t recommend it for Cathedral).
Emerald - 43.560
Reservorio - 1.58.268
Gran Pantano - 2.05.142
Gameplay footage (not my best driving - I didn’t know the course):
https://xboxclips.co/jezza14/675b55f0-98f6-41b2-95a6-c40236080327
Car 4 is selected specifically for this week, and the Ford challenge. The best S1 Ford is the GT 05 but that’s a bit dull. Running it a close second is everyone’s favourite FH4 drivatar option:
Ford Focus 17
Tune: GreetedDust8
Drivetrain: AWD
Tyres: Slick
HP: 959hp
The Focus is genuinely one of the best S1 AWD cars in the game. It is a little bit stiff in tight corners but has excellent acceleration and handles the more winding curves particularly well. It’s acceleration makes it a great all-rounder well able to handle most of the tracks FH5 will throw at you. This is a widebody version, so a bit ugly to look at in my view but if you want to take on the supercars, this is a good cheap option.
Emerald - 43.969
Reservorio - 1.58.510
Gran Pantano - 2.06.727
Focus v FXX and NSX:
https://xboxclips.co/jezza14/787e26da-f27e-4ffb-aa22-3f3b546dc9f1
