I recently purchased an 85 C10 305/350. The truck had been sitting for 2years. rebuilt the carb, installed new exhaust (w/o cat converter). Truck starts instantly, and idles very smooth. After driving for 5-10 minutes, it starts to bog down (no acceleration) and sometimes will stall. It will restart if pedal is held to floor during cranking. After a long rev to clear out the flood, it runs fine. Also, when letting off the gas (coming off free way speed) a very loud bang/pop will occur in the exhaust. There is also a constant smell of gas when parked in the garage, but the carb is dry inside and out. All vacuum lines have been replaced. Any thoughts? I've tried adjusting mixture and idle speed multiple times, but it makes no difference.

The bogging usually occurs at the same time the temp gauge begins to show the temp. After the restart it runs fine.