Does anyone have any ideas on why my Audi won’t rev past 4,500 RPM without breaking up (sputtering)? I am sick of this car!!!

I have dealt with this issue for over 2 years. The problem comes and goes depending on its mood for the weekend. We will fix something and it will go away, only to come back the next race. Then we will fix something else; again it will go away and come back on another race. Outside temperature does not seem to affect the car although the length of running time does. As a session continues the car gets worse and worse, breaking up more and more at lower and lower RPM’s. If you hit a bump in the past it has dramatically increased the problem. After the car comes in and sits for a half hour to an hour and cools off it will run better again and then progressively get worse as it did in the prior session. I would like to know EVERYTHING that could cause the car to break-up at higher RPM’s.


Thanks for the help…