I have a 351w with a c4 tranny in my 90 gt, it is carbed. The engine idles great "idle set at 950", until you put it in gear, then the idle drops WAY down and it will go dead unless you keep the idle up by keeping your foot on the accel. pedal. I have not been into the engine, but I was told that it has a lunati cam in it, and it has a alum. intake. When I bought the truck the forward frictions in the c4 were burnt up in the tranny, so I completely rebuilt it. I also added a TCI 2500 stall converter. I have checked all over the top of the engine for vacuum leaks and have not found any. I have to set the idle at about 1500 just to keep it running in gear, please help me out, this is about to drive me crazy. BTW this was the first tranny that I have built, it went very smoothly and I learned a lot, but I have to ask, I checked clearance with a feeler gauge during final assembly, if it was put together to "tight" would it cause this problem??