I have an 86 Iroc that came with the 305 vin F. The original owner swaped out the engine with a 350 block from 1974 and the tpi plenium from an 87 5.7 liter. I bought this car a coupl eweeks ago as a project. Now I am stuck. The first thing I did to the car after I bought it was I replaced the alternator as it was bad. about 4 days later my car started to stall at low speeds. I checked the ecm and Prom. They were for the 86 305. So the ecm and prom were trying to run my car off the specs for a 305 while it had a 5.7 liter in it. So I put a jet performance chip in the ecm and that fixed the stall issue. Now for a week the car drove fine. other than that i have to keep putting trans fluid in the car until I can fix the trani cooler lines to the stock 700r4 auto. After about a week the belt flew off the car. This belt routes around the crankshaft pulley, water pump and alternator. I have a serperate belt for the power steering pump. The a/c and AIR pump have been removed. The nut to the alternator pully had backed off and threw my belt off. so When i discovered that I put a new pulley and nut on the alternator with a new belt. I also replaced the battery since driving it for 3 days with no alternator killed it. Now the engine idles at 1250-1750 rpm in park or neutral. and about 750-1000 rpm in drive. I have no idea what the problem could be. and I can't tell if all the wiring for the sensors is stock or not. the original owner did his own wiring. Now I am thinking that the problem might be the iac motor ot the fact that I beleive that I am running with a fuel rail and fuel injectors from the 86 305. Any help would be great