Hello. I've got a 1987 GMC Suburban High Sierra R2500 with a 454 and a TH400, rwd. I bought it non running (figured that part out when it showed up on a trailer), which instead of having a qjet and a 700r4, had a stupid TBI and a th400, but it was all complete for the most part. Someone has been in this motor before, judging by all the orange rtv everywhere and new intake and valve cover gaskets. When I got the thing, it didn't run at all. I have since replaced the following: Plugs, cr43ts gapped at .035 per spec label on core support. new plug wires, no name but decent quality appearance wise. Map, coolant temp, IAC, and TPS sensors. Distributor. Timing chain. P/O said it was bad, it wasn't, but I already bought one so I installed it. Associated front end gaskets. The thing will start, and idle for about 30 seconds and during those 30 seconds it goes from ok to sounding like it's firing on 3 cylinders and it's just dumping fuel and then dies. I haven't touched the Tb besides replacing the sensors. I'm picking up a rebuild kit tomorrow. I rebuild qjets for fun, I'm sure I can tackle a tb. I also have a new o2 sensor to put in, the old one was jet black. and had some derpy spade connections on it. I also cut the rotten exhaust off (cat was plugged, muffler was more rust than muffler, etc) just before the cat. It also has started popping out of the passenger side barrel of the tb and expelling enough gas to land outside the engine compartment. I'm wondering if the fuel regulator diaphragm has ruptured. The new plugs I put in it are jet black as well so it's getting way too much fuel... Anyone have any input? and before you ask, I have tried setting the timing, but it has to be done on a warm engine, and the thing wont run long enough to even get close to operating temp.