Im trying to tune my yellowbird and i own a twin turbo that i cant install . I press the option to install it and nothing happens, however, i m able to install the the factory and the other turbo option. Please help.
I believe this is a glitch. I MAY BE WRONG but I believe you have to remove car from your garage and repurchase. Some cars dont seem happy when loading/unloading bought/ saved tunes
It is a glitch that has been present in the last several games (since the locking of tunes I think in FM3 or FM4).
While repurchasing will allow you to do what you like, is costs CR and doesn’t actually fix the problem.
It will have happened when you downloaded someones tune and applied it - often if this tune has an aspiration change you do not own already it causes this problem. To prevent it you can just buy all the aspiration changes before applying someone elses tune.
For the car that is already messed up the only thing you can try is to apply a tune from someone that has the aspiration change you want - good thing tunes are free in FM5 as you can try as many as you like.
Installing another tune with a twin turbo will solve the problem and afterward you will be able to install one on your own tune. I have had to do this a few times because of this annoying glitch.
Yes after reading this I tried this method on a car with this glitch and it worked! I can now install the glitched supercharger in my own tunes that I couldn’t before. The only problem is you can’t tell what parts are on the tunes you download, so you have to guess whether the tune you download has the right parts to fix it.
Thanks for the tip 
In FM5 the tunes are free so this is less painful than in previous games an still better than binning a car because the aspiration is glitched.
Thank you all for the info
It really bothers me that i have to get another yellow bird just for this stupid glitch. It is my first time playing a FM game and it will be the last one. I though I bought a serious game made by serious people and something so simple could have been fixed a long time ago since it’s been happening for so long in different game versions.
You DO NOT need another Yellowbird - just a tune with the other parts in it - do not waste your credits, just start downloading other peoples tunes until you find one with the right parts in it.
It’s happened to me a few times. I did not realize it could be fixed, so I have multiples of a few cars, but it’s nice having different tunes on their own car when playing multiplayer.
If you happen to want a top 10 RWD Yellowbird tune, I recently shared my current R874 tune called “RWD DRAG 19.517” (it will do 19.450 in the mile, but I shared it before getting that time). It does 7.733 in the 1/4 and 12.050 in the 1/2. Requires manual with clutch to achieve those times. Enjoy 