Ruff Idle ,Huge Loss of Power

[ZR2]

I have been reading / watching this thread with interest. Not trying to hijack it as I have a similar problem that has just emerged. Bought a 94 ZR1 awhile back and was stored for awhile, so I was doing maintenance, oil, plugs, filter etc. and after changing plugs noticed a stumble at low rpm's. Below 2000 was where it was happening. Car had NGK TR5IX plugs in it when I got it and I put in NGK BKR5EIX plugs and after about 50 to 100 miles the stumble started. It did not have a stumble with the original plugs, so I changed out the plugs this morning, they were a light gray to slightly white in color already, so I switched to a set of AC 41-800 plugs. I just came back from a short ride and the stumble is worse. I checked the fuel pressure on the engine and prior to starting it is basically 53lbs. I have waited awhile and it seems the pressure is holding, so I think the FPR is OK, I haven't changed the fuel filter yet and know I need to. Is it the heat range of the plugs possibly or probably a somewhat clogged fuel filter? Filter looks like a pain to change.