I have a 2001 Bonneville ssei.

5-7 weeks ago I had trouble with intermittent power. RPM's wouldn't fluctuate/flicker, but it felt like something could've been wrong with the transmission. Just a could days ago, about 15 minutes into my commute, I noticed I had drastically reduced power. It almost felt like I ran out of gas. When I lost nearly all the power in my engine, I pulled over. The engine runs super rough at idle; to the point that it dies. I'm getting the random misfire code on the scanner.

Any ideas? Anybody have this problem before?

To start with it sounds like an ignition issue meaning somewhere between the Ignition control module (ICM), coil packs, ignition cables, or spark plugs there is a problem.
To help narrow it down we would look at the code that you received p0300 = random cylinder misfire.
knowing this if it was just one bad spark plug or wire the computer would of given you a code like p0305 meaning cylinder 5 is misfiring and you could investigate from there. but you are receiving random misfire code so we need to focus more on the coil packs or the ICM. Most autozone and advance auto's are able to test the ICM to see if it is bad or not. The coil packs can be tricky to figure out which one is bad. I just always used process of elimination. I would buy a new coil pack and start by swapping it out and then take a test drive. etc. etc.

You also mentioned something about your rpm's flickering. If your RPMs are dropping out to zero while driving that is also a sign of your Crank shaft position sensor (CPS) starting to go. This sensor provides information to the cars computer telling the ICM when to fire the next cylinder. If this goes bad it too will give a p0300 code and a code for the bad CPS.

I would first check your ignition wires and spark plugs for anything obvious such as loose or broken wires just to rule that out. (If you havent done a tune up now may be a great time)
then get the ICM (this is the black circuit board under the 3 coil packs) tested since that is free if it comes back good... move to the coils.

If you need to get some good parts for low $ contact Andrew (screen name Harofreak) in the for sale section of the forum his contact info is the very first post. I ordered ignition parts from him and save me lots of $ over autozone.

good luck

I would also put a fuel pressure gauge on the rail and see if it is actually a fuel pressure issue. easy to check and will eliminate the fuel pump.

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Shane "RedZMonte"
2004 Z16 Z06: Virgin
2000 SSEi: Kenwood DDX512, 3.25" MPS, ZZP DP, PLog, Puck Mount, NGK TR7's, DHP Tuned
1995 Monte Z34: T04e "60" turbo, 42.5# injectors, Borla Catback, OBDII swap, DHP Tuned, Much more...

I had a simular problem with my 2000 buick lesabre last year out of the blue it ran really bad no power at all and just would barely
run at idle i changed my plugs and wires they were old that made it run better but did not fix it so i used my inductive timing light
to check each spark plug wire for spark i had no spark at 2 and 4 was running on 4 cyl so ithought it was the coil pack replaced that
still not the problem so i checked the icm for voltage and switching signals well no switching signals at 2 and 4
went to pull a part got a icm off a impala i think it was a 2002 cost $22.00 runs like new just a thought

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2002 Bonneville SE
2000 Buick Lesabre Limited
65 Tempest Club Coupe (gone but not forgotten)