i searched, but could not find the answer.

at 5500 rpm's, it just stops going, spits and sputters , in gear, in LOAD, in nuetral.

need help

Year/Model? Mods?

s4 swap in a b2000, stock ecu n326, emissions removed, header, 6-port removed, rebuilt harness.
idles good, solid

Glad I asked. What ignition setup are you using? Does it seem to be a breakup problem, or does it just hit a wall? ECU/injector grounding could also cause similar problems.

check your ignition...but i think as said your problem could be ecu or injectors..I would think 3500 stumble would be injector pulse? but at 5500 i am not sure

so i swaped afm's and it will pull to 6k now, this is a build and i used 3/8 fuel line feed. is that size of line to big for the stock pump, curious if i'm losing pressure from the size of line?

when driving, i hit 6k and it seems the same, but not as bad. but i do get white smoke(from what i can see in the rearview) when it is 6k and not wanting to go farther.

comments please!

Stock fuel lines are 5/16", so you are running a little larger diameter tubing. Testing fuel pressure is relatively simple. The specs are in the FSM, but you'll want to see roughly 40psi when the engine is at 0 manifold pressure. Popping the vacuum line off of the FPR at idle, or with the test connector jumped & the key to 'ON', will simulate this. The AFM will supply the ECU with the air volume measurements that lead to injector duty cycle, so it's sounding more like it has to be fuel delivery related.