I have a 1990 gxl with a jdm turbo II s5 swap. I have a racing beat three inch down pipe, hks blow off valve, electric fan, custom drive shaft, and some emission removals. My problem is this, the car runs amazing . Im hitting 90 in second the car pulls like crazy and is just great. Ill warm it up for fifteen min then drive, temp gauge is at half and it runs great. BUT, i take it on the high way for five min then i get off a exit and it drives horrible. i have to take it up to three grand and slowly drop it to get it moving. it drives like i have the spark plug wires mixed up after that. this is so annoying cuz the car runs so great for the first fourty min or so then just is bogging down and bucks alot. also it wont hold a idle when i let off the gas. when i come to a complete stop it seems to die. i been building this car for six months now and its just getting on my nerves but cant get rid of it cuz it runs so good at first. i also have a fuel cut chip on it. please help me. i cant tell you how much this just pisses me off.

 

Maybe the blowoff valve is sticking open? or bov related in someway. As in Air Leak.

 

Do you say 90 MPH in 2nd gear? That should be a problem right there.

 

As in, it's seating good after the car has been sitting a while, but once you drive it and make boost etc, maybe it isn't seating after blowing off? Just a guess and nothing more.

 

but why does it act like its spark plug wires are on wrong and it sounds like a train? ba babababababa all three the rpms?