In neutral, I try to hold 2K rpm... It won't hold it steadily. The rpm hit at 2K for a sec then a sudden pop, rpm drops to 1800, and catches itself, and goes back to 2K.

Anyone have any ideas what may cause this?

So far... I've replace the fuel filter, cleaned the air filter, new spark plugs, dist. cap and rotor.

More info about the motor... stock b18b, intercooled, turboed, dsm 450 cc, converted to obd1 @ running 8 psi.

My gas mileage sucks. If I stompt on it, it accelerates good. If i coast at say 40 mph, there is a pulsation. Maybe related to the rpm drop in neutral at 2K rpm.