Framedrops and bad frametime. CPU usage is not right! Core 1 @ 100% all the time.

OK, I have a good PC. A i7 4790 a GTX 1080 and 16GB Ram. I play on Ultra-4x Msaa @ 1440p
The game stutters from time to time and i dont know why. I think it stutters, becuase it uses one CPU core at 100% all the time. Forza Horzizon had the same problem. After a patch we could use all cores and the stutter was gone. I thought the Turn10 optimised the game for PC gamers.
It runs @ 60fps most of the time but it also drops to 40fps with very bad frametime. I happens without a reason. I am in front no cars behind me or in fornt of me, everthing is ok and suddenly a big fps drop to 40 for 2-3 seconds.
I closed MSI Afterburner nothing changed. Low,mid or high always the same problem. I want solid 60fps with solid frametime.
You guys said you learned a lot from Forza horizon 3. Where, I dont see it? Do we have 2 wait 3-4 months for a patch? Forza Horizon runs better then the Forza 7 Demo.
I think i will wait, and i can’t recommend the game at the moment.
I hope you will fix this.
Thank you!

I agree with the poster above. I previously installed Forza 6 Apex with the hope of getting a feel for the newer Forza games (I have not played Forza since Forza 2 back in the Xbox 360). I noticed the game was full of stutters in game, tried doing practice rounds but still experienced the same stutters. I played around with every graphical setting and still experienced the same result every time. I even went as far as installing the game on my new fast SSD, but no dice. The stuttering still there. The best way I can describe is like a small freeze for less than a second which breaks the immersion completely. I experienced this in my older 4790K, GTX 980ti, 16GB DDR3 system, and now am experiencing the same problem with my new 7700K, GTX 1080ti, 16GB DDR4 3200Mhz ram system. Its so silly.

Forza Horizon 3 used to run like rubbish, but now it runs like an absolute dream. I tried this Forza 7 demo hoping and praying that these small stutters would not follow through, but what a suprise, they seemed to have made it into the demo. Some people have reported these stutters with Forza 6 Apex, but it never got reviewed or fixed. In fact, most of the time people were blaming their systems instead of the game which is silly since I have had this happen on two completely different builds. I hope this gets sorted, as I want to buy this game, but will not accept this mediocre level of care for PC. I will make sure to spread the word about this as this needs to be reviewed ASAP.