Goin70

I posted this on the C3 Tech Forum, but thought there might be an expert on this Forum that doesn't comment over there --- I have an LS 376/480 crate engine in my 1970 Corvette restomod. The engine runs great, but I'm experiencing a "popping" and "crackling" sound when I decelerate while the car is in gear. Sometimes, I even get one or two "backfire" pops. What is causing this? Can it be tuned out of the engine? The car has a stainless steel Magna-Flow exhaust system that has been installed by a pro, so I know there's no flow obstruction or other problems. Could it be inadequate air intake through the K&N filter setup? Help ...

HOXXOH

I had a similar issue caused by the iridium tips of the spark plugs breaking off, which created an .080 gap where it should have been .040. I assume you've already checked for manifold leaks and the AFR is in range.