Hey guys, my car is a 2002 Bonneville SSEI with 79k miles. I was accelerating to highway speeds today, and all of a sudden the car began to buck and jerk like crazy, initially thinking it was transmission related, I pulled over and in doing so, the engine stalled out. It wouldn't restart normally for a couple minutes, but then it finally did and acted normally the rest of the drive to work. Now the car (usually) starts right up fine, let it idle and a slight skip can be felt, but when I play with the throttle it begins to misfire, bogs down and eventually stalls. Give it steady throttle and the CEL will flash at about 3k rpms. Long story short, I have a P0301 and P0420, there is some black smoke coming from tailpipe when it'* running rough. I replaced plugs and wires about 2-3k miles ago and replaced the coil pack associated with cylinders 1&4, with no results. I did fill up with gas very recently..could it be bad gas?
Does anyone have any suggestions what it could be or what to look for?

Bad gas would cause a misfire on all cylinders......

Well, I would get a spark tester, and check the output of #1 plug wire, and then #4 wire.....also look for carbon tracking on plug, or carbonning at the tip of plug, and inside the boot at the contacts of each plug wire.....if ok, let'* see if it is #1 cylinder causing the misfire....raise idle until you feel the misfire....now disconnect #1 injector and see if there is a dramatic rpm drop off....compare to #2 and other injectors when doing the same ting.....no dramatic difference, with the injector disconnected, is the cylinder.....

Outside of an ohm reading, testing injectors involves expensive equipment....can try swapping the injectors in the rail, and see if the misfire moves to another cylinder.....

Remember, when you have a misfire, the O2 sensor sees unburned O2 in the exhaust, and enrichens the mixture, compounding the problem....

P0420 looks like a cat on it'* way out......

Solved! Thank you for the input, it turned out to just be a bad mass airflow sensor meter. After I installed it the check engine light went off and after stalling once or twice it cleared itself up and now is running great! The car shifts a lot better, no shuddering, and idles like it should.

Thanks for following up with the fix!