got a 93 camaro with a 3.4l and every now and then it backfires out of the intake tube. it has no power it wont rev over 4000rpm's it has no power at all. i put a new tune up on it, new map sensor, new tps sensor, injector o-rings, new crankshaft sensor, and intake plenum gasket the ses light is not on,replaced the catalytic converter with a straight pipe. any suggestions?

please help im tired of putting money in it