so ive had my sportster for about 2 years now, other then normal maintenance i added the stage 1 screaming eagle tune and ive added taller handlebars, got a switch kit from harley so no soldering or anything, crimped pins to the connectors. only ridden 6 times in the last 5 months, and lately its been popping and missing, and backfiring, rough idle, it will idle on its own but will eventually die. first thing i did was replace the plugs and wires, and even replaced the intake gaskets going into the head. Still doesnt run right so need help on where to look and what to test now. i have the service manual but it just shows how to replace parts not troubleshoot them. the tune was done right after i bought it and ran great for 2 years until now,