looking for the problem. I have a 65 chevy pick up. 2wd, 4 speed, stock bottom end, stock pistons 30 over, pro comp aluminum heads 2.02 1.6 roller rockers, 488 292 cam, performer intake, 650 edelbrock with manual choke, headers into flowmasters. the truck backfires through the exhaust when i let off the gas, driving in town at low speeds and at a idle. I have checked timing, valve adjustment, vacuum leaks and exhaust leaks. I dont know where to go from here. if anyone has any ideas, i would be very greatful. thanks  

Welcome to the forums, can anyone help fleetsite with his question.  

mpayne, who turned you into the message board traffic cop?

Probably since the thread author used a cam at least 20° too large all that unnecessary overlap is wreaking havoc with the spent gases on deceleration. Unburnt fuel (caused by a poor cam and a drastic reduction in the engine's fuel needs) and small amounts of fresh air are probably igniting in the exhaust - it's not uncommon.