1989 Pontiac Firebird rough idle, no power

8/3/10 My car was went from driving awesome to driving poorly in the matter of an hour. Car was driving fine, got gas in it and came home. Went to start it 20 minutes after shutting it on my driveway. The car was idling low and seemed like it wanted to stall. I was told a year ago that I had 4 injectors that needed to be replaced. 2 were bad and the other 2 were really bad. I could only afford to do the really bad ones. This made the car drive awesome. Thinking the other two injectors went, I replaced all the remaining ones to play it safe. Finally got car started and it sounded bad. It stalled a few times but figured that was just because it needed time for fuel to cycle through.
To my dismay, the car purges, and sounds good when you hit the gas in park. When you put the car into drive though, it sounds like it is going to stall and has no power. Needless to say, even with new injectors in the car, new fuel pump and fuel filter I can not get the car to feel reliable. The fuel filter and pump are about 6 months old at most. They were not replaced at the same time as the injectors.
I NEED HELP to get this car reliable. Do you think it is timing? Bad gas? Fuel ratio? I am at a loss.

Please Help! Thank you

8/4/10 ok, update. There was a vacuum line under the plenum that was blocked off with a screw. When putting everything together, I reconnected the hose. Today, I blocked the hose off again and it seems to run a little better but transmission is not shifting right. I am thinking this has something to do with one of the vacuum lines.