I just got my 383 SBC up and running again. I'm using Holley's EFI system with computer controlled timing. I think I may have my timing off a bit. I'm getting a loud pinging/popping sound from the engine whenever I try to give it gas when the RPM's are real low or when I gas it in a higher gear. I don't see anything out of the norm with my timing. I feel like I've had this problem before but I can't remember how I fixed it. Any advice?