Ok this might be a little difficult to follow, but I'm going to try my best to explain whats wrong with my car. Sometime when Im crusing at say 75 mph in 6th gear, I sometimes notice a slight bog/ surge where it feels like its hiccuping..watching the tachometer, when it sputters, the revs bounce around a lil bit...usually around 500 rpm. So try to think of it this way..6th gear at 75 mph, holding steady at 2,500 rpm, then it sputters and the revs jump up for a split second...its really erractic. It will sometimes do it in 4th, 5th as well at different speeds, and the car feels a bit slower that it was. Has anyone seen that before? I dont know if its spark or fuel related, but I just got my car back from the shop 3 weeks ago after they used tunerkat to fine tune the car. I am using a cartech FMU that pushes up to 85 psi of fuel pressure to the 42 lb injectors. Ive got a 255 intank pump and vortech inline booster pump too. Im really confused and have no idea why the car is sputtering and why my tachs acting funny?

 

Do you have a fuel pressure gauge on the car? I don't know at what level your injectors will "lock up", but 85 psi is certainly pushing the limit.

 

Do your light screw up too? might be an ingnition switch.

 

Maybe a shorted or bad ground wire to the coil.