Non-Mustang Car Help

Hey everyone! I've got a really crappy running 1992 Pontiac Bonneville with the 3.8 V6 in it (I know, I know, its not a mustang, but you guys know your stuff). Just about every time I hop in it to drive, it starts right up without a hitch. If I rev it up a little it falls flat on its face and usually dies after surging for a while. Sometimes, the more I press the gas pedal the more the engine bogs down until it dies. Even the slightest engine load seems to make it fall on its face too; I can't even accelerate. I've held the gas pedal to the floor before and it slowly gains a little speed but seems to top out at 20 or so. When I do get it up to speed (when it is running correctly) it will start acting up and the car with stutter and shake. When it is cooler out, say 50's or so, it doesn't seem to do it, or do it near as bad. When it is about 70 or warmer it does it all the time.

I've replaced the plugs with some Bosch platinums as well as the plug wires. It didn't help, it may have made it worse, but it is really hard to tell. The old plugs had a little white to them, but nothing out of the ordinary I don't think. I just put a can of Berryman's fuel injector cleaner in it in case something is clogged up, but haven't ran the car since. The car did sit for about a year and it ran fine after I got it out. This crap started happening right after I filled the tank up second time.

My cousin thinks that it is the coil packs, but I don't really want to drop $100 on a part that may not fix it. So, what do you guys think?

Thanks a lot!

Opps... sorry about that!

I originally thought of the bad gas, but I filled up at BP the second time and have heard that their gas is usually good stuff.

I've gotten one CEL, but otherwise nothing. I'll have to see if I can hobble it over to a parts store to grab a code reader. I imagine it is like a stang and will store codes that don't throw CEL's.