I recently had a Turbo Back Exhaust installed on my Evo 9. Before I had it, I could run 3rd gear to 80mph. Now it's hitting about 75 - 76 mph at redline in third. What is the reason for this?

 

At the risk of sounding unfriendly, thats quite impossible. The only way that you can change top speed at any given gear is by either (a) changing the actual gears in the transmission or (b) changing the rev limiter so that the car can go higher or lower on a certain gear.

 

Well, maybe it's me misjudging. But it just seems like I have to ride it further into the red to hit 80 mph. Couldn't this occur if the clutch slips, though?

 

Are you sure it isn't hitting the fuel cut off early?? Sometime getting a TBE without a tune will cause you to overboost and the ECU will cut the fuel earlier like say 6K.

 

No, the clutch would slip at peak torque, which is down at 3500rpm. It won't slip at 7000rpm, because the torque is way lower up there.

 

Your ECU could be pulling timing with the new mods you have. That could explain why you aren't putting out as much power at the same RPM.

 

Even with less power, his MPH per RPM would not change.

 

+1 Top speeds per gear are an entirely static mechanical function. Its like a telescoping antenna, it doesnt matter how hard you pull, the antenna is always gonna stop extending at its physical limit.

 

Aftermarket wheels maybe???