Ok so my car has been acting up lately and me and my buddies cant seem to figure it out so ive turned to the internet for help.

My car breaking up in first and second gear under wot around 5k or after and when boost starts climb?
At first i thought boost leak but it seems to run fine 3rd, 4th and 5th wot
it almost feels like fuel cut because it bucks really hard

S13 sr20det black top
here a small list of what ive changed....
New plugs ngkbkr7 gapped to .030(haven't tired .028 yet), coils, z32 maf, igniter, fuel rail(oem), fuel pump(mk4 tt), fuel pressure regulator, injectors(740cc) and ecu(tuned for 740's) both coolant temp sensors and thermostat. Running only 10lbs of boost on a new gt2871r .83 trim.

compression from the front to the back of the motor is 150, 149, 149, 135 :/ maybe a ring problem?

 

All grounds seem to be in check

 

Low compression in one cylinder shouldn't cause a breakup at high rpm. It's also within the 14psi factory limit. I'm thinking plug gap isn't set correctly or spark arching from cracked coilpack.

 

Coil packs were brand new. As well as brand new plugs gapped to .030.

 

Try gapping down to .028 and go over your grounds, and make sure you don't have any vacuum leaks. I mis-grounded an intake manifold ground for my injector harness and lost fuel to a cylinder. They are really important.

 

something dump like dying fuel pump not keeping up fuel pressure?

 

New supra mk4 tt fuel pump just because wasn't sure if the walboro* was pushing enough out, new fuel rail and regulator