Pontiac Repair: My car lacks power and is getting worse..., fuel injection systems, model pontiac

Question
Well I have a 90' model Pontiac Formula with the 305(350?)TPI. I rescently made a short trip roughly about 140 miles and half way there it suddenly lost power and spit and sputtered and I pulled off where it eventually died minutes later. I waited about 2 minutes and it fired right back up and I drove off with no problems. I figured it might have been a shortage of fuel in the tank but much to my dismay it had 3/4's of a tank. It ran good all the way to my destination. On my return is when it started. I would try to accelerate and if it got half throttle it would bog but not die.If I let off a little it would sort of pick up but engine power for it was gone. I eventually limp it back to my home town all the while going 50mph the whole time. It threw a code coming back and when I had it scanned it threw a 12 and a 45. I replaced the TPS and the MAP and still nothing. I purchased a fuel filter cause it has roughly about 270k on it(not hard miles at all and its had Royal Purple in it its whole life:) I'm absolutely stumped! I've had all kinds of Chevy's most of my life and this one is kicking my butt. HELP! It seems as though its getting worse and I'm not for spending any more money on this thing until I figure out exactly whats going on! I've looked all over the e-net and I have come up empty handed after many hours of looking and probing. Any help would be appreciated! R.

Answer
Hi Rick:

well the 12 is not a code it just let you know your into OBD diagntice code check. the 45 is for a rich exhaust. I would assume if it's a formula it is a 350 with TPI not a 305 wit TBI?? It makes a difference 2 completly different fuel injection systems. if indeed it's TPI engine try this when it's running poorly unplug the MAF sensor it's loacted in the air tube betwwen the air cleaner and the engine and see what happens. it will hesitate but it shouldn't bog down like you said it is. there are a lot of other things that this could be as well but with out an actaul scan tool your just going to be guesing as to what the issue here is. Another thing to look at it in the distributor the pick up coil and the timer core on the distibutor main shaft. the pick up coils go bad over time the insulation breaks down on the wire and it will short out with the engine heating up. The main shaft on the sdistributor has a magnet on it which is what triggers the pick up coil ovre time the magent looses it's magntism and it will cause a false RPM signal to be inducted into the pick up coil. just a few things to look at. The main shaft thing is an oddity but it does happen especially after years of heat cycles.