I have a 1987 325.
When I start the vehicle is revs up to ~3100 rpm. after ~15 seconds it begins to change from ~2200 rpm to about to die. after long inspection and trouble shooting we thought we had what was wrong... turns out we were wrong. We drove it around maybe half a mile or so and when it drives with a load it will change from ~2000 rpm to ~900 rpm up and down... so on.
We've begun to narrow it down to possibly a fuel problem because we don't think it's a fire or vacuum problem.
Any assistance would be greatly appreciated!!!