Not sure what to call this other than moody bogging issue. Ever since I bought my 1999 GST my car has had a really weird bogging problem. I start the car and it runs fine and normal for a few minutes, but then the RPMs drop super low and it starts idling really really rough like it's having a misfire. After 5-10 minutes the RPMs jump back up to normal levels and I can drive it like it never happened. Even if I start it and start driving, after a couple minutes it starts lurching and loses almost all engine power and I have to pull over. I wait for a bit, the RPMs normalize, and I can keep driving.

I've got a few theories: fuel pump, fuel filter, Spark Plugs, bad engine ground maybe? I've replaced the fuel pump and that really helped, but it still does this every now and then. I also put in new spark plugs and wires. Could be the fuel filter though, or a bad engine ground (I do have a lot of wiring problems...). It is worth mentioning that I used to have a battery master switch because my battery would die from parasitic leaks, and that I believe increased the frequency of the issue, but I don't have it on the battery anymore.

Thoughts? I can't figure this one out. I can post a video of it happening too if that helps.

Thanks!