Ok guys, break out your reading glasses this is going to be a novel...

So I bought a 2003 GTP with a blown motor (no big deal) and rebuilt it with all new rings and bearings and new heads and got it all together and once I fixed an injector wiring plug it ran like a champ. Driven it for about 1200 miles not and not a hiccup until about 2 days ago. I noticed that one day when I went to start it it struggled, it fired off fine but struggled to get to idle RPM. It would bounce between like 500-1200 rpm for about 2-3 seconds wanting to die and then would idle a little high and a little rough. Not bad at all, but knowing how a motor should run its ever so slightly rough. It does this almost everytime I start it (wanting to die) sometimes to lesser degrees, but always has a higher idle. Car drove fine - so I thought. More on that in a min.

Then yesterday I was waiting for a buddy of mine and was just sitting in the car listening to music and then I went to start the car and it popped to life, then about 1-2 seconds later died, tried to start, fired off then died, did this once more before I started it and gave it some gas and then it got going and stayed running (idle about 1000-1200 rpm or so). Kinda thought this was a little odd. well on my way home about an hour after this it through a CEL. Got home and checked Codes and had a P0171 (bank 1 lean) so I started looking for vac leaks and basic sensors (MAF and TPS). TPS seems to be working fine (scanner readings) unplugged the map, and plugged it back in and the car did all kinds of odd things for a split second then returned to its usual. So I atleast know the MAF is working. I swapped out the front O2, no change, covered the motor in starter fluid trying to find a vac leak and nothing...

By this point i'm getting a little annoyed seeing as how I should've been in bed since I get up so early so I ran down to a buddies house to get some advice (dead end) and then on my way home I was cruising about 35 and punched it to see what would happen. (maybe 50-60% throttle?) and the car fell on its face. didnt die, but just sounded plugged up. going up hills or using any torque around the 1500 rpm mark the car bucks real hard too until it down shifts to 3rd then it gets its **** together. By this point the CEL is now flashing (must mean good things right?) so get home and pull codes again, and now there is a P0300. Last ditch effort I throw a fuel pressure gauge on it and key on 45psi, running at idle 41psi. I know this is SLIGHTLY low but cant imagine it would make THAT much a diff?

Going to replace fuel filter tonight, but other than that I just done know....

(oh the car is a 2003 GTP supercharged)

This all being said I'm now at a loss.... Please help. lol

Thanks fellas!