I have an 07 Softail Custom with SE AC, V&H staggards, and V&H Fuel Pak. I had all this done before I picked up the bike at the dealer. Lately, after I park the bike in the garage after a ride I smell fuel if I have to return to the garage for any reason. The bike also backfires (pops) once in a while after shifting to an upper gear.

 

Sounds like you're bike's running rich. The popping seems to be pretty common with the FuelPak.

 

close the fuel cap? lol Lots of times you'll have some unspent fuel in the system...No biggie.