1990 Corsica lacks power and backfires

I have a 1990 Corsica with a 2.2 Ltr and it has 135,000 miles. The car was stalling all the time so I replaced the O2 sensor, MAP and Crank sensor and the car no longer stalls when it warms up but now the car has no power and back fires when I try to accelarate. It also idles a little rough with an occassional spudder but doesn't stall. The back firing is out the tailpipe.

Any trouble codes since the other parts replaced? May be a EGR valve goofing up, or, possibly a vacuum leak. Might also clean the IAC valve as that can cause some problems with rough idle.