I seem to be having a rich problem that I can't seem to get rid of. Fuel presure good, O2 sensor works, all sensors seem to be functioning. Runs strong up to @4000 rpm then falls flat until @5200rpm. After 5200 it goes back to normal. WTF WTF WTF!!! About to trade it for 4th Gen.

Insert 2cents!!

 

check to see if the engine is trying to tell you whats wrong by checking the codes if its not giving you any codes and being stubborn check fuel injectors or just save time and ahve a tech look at it.