I have put a set of Vance & Hines Straight Shots on my bike and can not find any info on fuel management. Buddy at the bike shop wants me to put on some electronic gadget for the low cost of $200 odd bucks plus 2 hours installation. My issue is I am getting some backfire going through the gears up and down. Bike shop Buddy says that this will still happen with gadget installed.

All I am looking for is to get the best mileage and to make sure bike lasts. There is no smoke and the color inside the pipes looks normal.

Any ideas?