My 2000 Heritage Springer will consistently back fire during the first start up of the day. The back fire occurs the instant in which the engine fires up. It only does it when cold, at any time of the day, even when sitting in a 95 degree garage. It rarely does it after the bike has been running. It does it with the choke in or out. I always press down on both compression releases. This only began to happen after I installed an all OEM Harley-Davidson headers and mufflers exhaust system. It has dual, fish tail pipes and mufflers with a cross over pipe. The mufflers have factory baffles. In 2018, one of the previous owners installed a 107 ci Screaming Eagle CNC ported engine with carburetor, and a six speed transmission. Also installed at that time were Tru-dual Vance & Hines headers and mufflers. In addition, it has a Dana-Tech adjustable electronic ignition system with rev limiter. I suspect it is running either lean or rich. I suspect that it was all previously programmed to run with the Vance & Hines system and now may need some adjusting with the OEM exhaust system. I know nothing about carburetors and don't want to mess with it and screw it up even more. I will be taking it to an indy shop to have it looked at. In the meantime, I thought I would ask for an opinion as to what you all think the problem is. The carburetor has what appears to be an extended adjuster with a twist *** at the end hanging down one side of the carburetor.

 

I forgot to add: I have a Screaming Eagle high flow cone air filter. I have been using the cheap, low octane regular gas (88). Should I use Ethyl (high octane 94?)