i purchased this car back in may , its a 92 firebird 305 tbi automatic before i bought it the car sat for a few years so after a new battery i found it needed a fuel pump so once i finally got it running it idles around 1200-1500 and will not rev past 2800 rpm and starts to misfire but it wont mis at idle , when driving the car it has no power.it also runs rich the exhaust is dark and will leave black spots on the driveway from just sitting at idle. i put in new plugs and recently chopped the exhaust just before the cat to see if that is plugged and it still ran bad. what could be the issue?

 

my car had a similiar issue when i first got it, it wouldnt rev out just kinda load up i gave it a good tune up, a couple things i would check that helped me were the map sensor, mine was giving me a long crank hook up a voltmeter and apply vacum to it via a hand vacuum pump and watch the voltage it should change in a linear fashion and jumping or sticking in the readings could indicate a bad sensor, also check the ect sensor as they are a very high authority sensor on tbi engines