Hey,
After receiving several suggestions about deceleration popping from my pinto, running lean etc, this afternoon I inspected the carb. It was modified by an engine builder when the motor was reconditioned. From what I can see so far it's had choke butterflies removed, anti dieseling valve removed, primary and secondary main jets have been redrilled and the original size stampings filed off, and lastly the idle mixture screw & spring has been removed and plugged with what looks to be a plain screw. I haven't tried taking it out yet.
The head has mild street cam and double valve springs. As mentioned there's deceleration pop when I back off the throttle. Other than that it's runs great.
Any suggestions? Thanks