Please help!
 

I have a '99 S15 2dr. Last year I installed K&N intake, Magnaflow 2.5" converter and muffler, E3 plugs, Taylor wires, Accel coil, and AC Delco cap and rotor after I upgraded to new style spider injectors and replaced IM gaskets. It worked great for 4 months. Now if the revs get up to 3000 or drops out of OD climbing a hill after about 5 secs it starts to bog really bad. If I pull over it huffs and puffs for about 10 secs then clears right up. I have installed, new fuel pump, fuel filter, all O2 sensors, TPS, MAF, MAP, PCV, Purge and vent solenoid, CTS, and crank sensor and it still does it! I swapped back to original coil and old cap with new NGK plugs and it still does it. Could it be my ECU? Could the new crank sensor be bad? I can hear gas dripping back into gas tank after shut down so could it be the regulator? All vacuum lines look good. I'm stumped and ready to give up.

Anybody? Anybody at all have an idea?

sounds like your cat is pluged

Lotta things going on here. Not sure why you would replace all that stuff, and not use AC Delco, (better quality and cheaper). These things are very fussy when it comes to tune up parts, and they don't like aftermarket.... at all;)

If the crankshaft position sensor, (and or timing cover) are moved, removed, replaced, or disturbed in any way, the crankshaft position sensor relearn is mandatory. If it is not done, ignition timing and injector timing, (among other things), will be incorrect, guaranteed. Reinstalling the original sensor still requires the relearn to be done. The procedure is done with a scan tool capable of initiating the relearn. Once the vehicle is programmed into the scan tool, the relearn literally takes less than 5 seconds to complete.

Extremely doubtful the PCM is at fault.

Check regulated fuel pressure and leakdown. Connect a pressure tester to the service port next to the distributor. Key ON, engine OFF, fuel pump running: pressure must be 60psi to 66psi. It must remain above 55psi for at least 10 minutes after the fuel pump shuts off. Post the results.

Yeah I thought my new cat might be plugged also. So I cut it out and welded in another one and still the same symptoms. I will try the crank sensor relearn I guess at the local dealer. It sure seems like a fuel problem above 3000rpm. All sensors and the injectors are Delphi which I've been told are as good as Delco. I always use Delco caps and rotors though. New fuel pump didn't change symptoms but I will check fuel pressure. I'll try to get someone to scan live data as the symptoms happen also to see if something shows. Thanks for the reply guys!