OK, here's my sad, sad story. BTW, I was just told about your site, so I hope SOMEONE out there can help. I have a '91 suburban /forums/images/graemlins/burb.gif that had the stock 350 TBI motor replaced this past March from a specialty engine swap company. The truck is a 2 wheel drive, posi rear, automatic w/ overdrive rigged to tow. From day one after the swap, the truck did not run right. To keep this thread short, here's what the truck is currently doing.... >Very rough idle from a cold start >poor gas mileage. dropped to 12 from 18 on the hiway >Once truck is at operating temp, w/ the truck in gear and foot on the brake, like at a stopsign, the engine RPM's will drop occasonally (from 700 to 400) and will occasionally cut off. >No power at higher RPM's (freeway driving) >The most bizzare issue happens when you have the brown/black distributor wire in place and a timing gun firing at the timing mark on the pulley. When you give it gas and rev the engine up to 3K RPM, the timing mark will advance and then immediately drop back down. The timing will not stay advanced for power. >The hydrocarbons read very high for a new motor, in the 125 to 140 PPM range. The guy at the inspection shop said for a new engine, it should be around 30-40. This states the engine is running fat. As far as the engine goes, the long block was replaced. Over the past 8 months, the following has been replaced.... >distributor >starter >knock sensor >O2 sensor >coolant sensor >ECM >TPS >main computer and PROM >PROM has been replaced w/ hypertech chip >coil >plugs, wires and cap >TBI pressure regulator, seals and injectors >vaccum line running to MAPS sensor I'm at my wits end. I'm really close to having a great bon fire in the back yard w/ the suburban as the center piece. I like the truck and bought it tow my travel trailer, but I can't stand the way it drives and mileage is killing me. Any suggestions at all???? HELP!!!!!!!