I have done a lot of searching around on this and other forums to get me where I am at on this issues, but I am still having some code 33 issues on my 92 3.1L firebird. Here is the story:

1) The car had been sitting idle for ~2 years, but after replacing the battery and changing the il it was running just like the day I stored it. Which is a fine condition.

2) I replaced the distributor gasket to help fix an oil leak and got a new cap and rotor while I was at it. After that I drove the car and it just had little to no power, I had to floor it to get up to high way speed. However, the idle speed seemed very smooth, which was nice. I also noticed my HVAC would switch to defrosters if going over 40 mph.

3) Thinking it was a timing issue, my dad and I set to fix this. We had no timing light at the time so he set it by ear. We also reconnected the HVAC vacuum line, replaced the vacuum hose leading to the vacuum resevoir, the small hose coming from the throttle body to the fuel pressure regulator, and the small hard vacuum line going to a part next to the EGR that i do not know the name of (anybody?). After I drove it, the car then idled fairly rough and would stall at stops.

4) Next I set about looking for vacuum leaks and correctly setting the timing. I did get the car set to 10° BTDC and have not yet found any vacuum leaks. I tried carb cleaner and soapy water with no luck. This did not fix the problem but did help to get the idle smoother. At this time I also sealed some leak in my "cold air" intake kit and i noticed that I could actually hear the intake pulling air, which I never could before. (I am going to double check this when I next get a chance to make sure I did not introduce a leak)

5) Next I replaced the entire distributor and IAC valve and tried the idle re-learn process. A test drive afterwards showed no stalling at stops, but the car would not go slower than 35 without me applying the brakes. Hoping it was the MAP, i replaced that too. I then took it for a more spirited spin, but when I hit the brakes for a stop light after going ~45mph, the car stuttered and died. I was able to limp it home after many restarts at every light, ~1.5 miles.

6) This weekend I confirmed the timing was still at 10°BTDC, so no issue there, replaced the PCV valve and double checked the vacuum lines (which do match up with the vacuum diagram). I found that the small line from the throttle body was pinched off, so I replaced that and double checked the vacuum resevoir, which did not show any leaks. I then ran sea foam through the brake booster line, and eventually got the car to idle for a while and burn off most of the gunk. It was still running a bit rough. The last thin I did this weekend was pour in some STP heavy duty injector cleaner. After 30s of running it stopped and there was smoke from the throttle body, but when I restarted it, it was running smoother than I have ever heard it. It ran that way for a good 15 minutes before i had to call it quits.

I am going to replace the plugs with autolite platinum (currently BOSCH 4+ that are looking pretty bad) and replace the fuel filter during a soon to be done oil change. I am wondering if it may be the injectors causing my code 33 by just not letting the engine produce enough power and therefore vacuum. Does that seem possible or should I still be looking somewhere else?