Very well could be the intake....I ran a single plane, a Team G, a couple years ago...Now that you mention it, I had a popping sound at cruize speed too....I know everything else was OK. I run an RPM Air Gap intake now, and no more popping sound. Maybe it's just that. The single plane is made for higher RPM operation, and the air/fuel mixture distribution at lower flow rates is uneven cause it's being pulled from a commom plenum (big area) by all eight intake runners. When you get on it, it smooths out like it should. If you have the ignition covered, and the carb, it cant be too much else. If it hasnt been run in 10 years, maybe just some miles on the engine will help smooth things out too. Enjoy it!! My engine is still in the shop being bored and decked, Im looking at another 3 weeks at least before my 496 is done. I cant wait, spring is here.