Motorcycle Repair: backfiring out of exhaust, 1994 suzuki gsx750f, fuel ratios

Question
i have a 1994 suzuki gsx750f katana. long story short the bike had been sitting for several years before i got it, so after i went through everything i had my mechanic go through it. at the time the back firing was not an issue. but now i guess since its been ridden more any junk that was in the carbs is getting flushed out and throwing off the sync and air fuel ratios? it backfires on engine breaking, but it doesn't do it nearly as much when its on choke. also when i take it out on a longer ride the idle will go from the normal 1200rpm setting to about 2000rpm. right now im trying to set the idle lower so that doesn't happen but in the meantime i use the clutch to slow the idle down while im at lights. keep in mind that this bike does have a aftermarket mild camshaft (i did not put it in so i  do not have the specs) as well as a cobra f1r exhaust. what should i do? re-sync the carbs and keep adjusting idle?

Answer
Ben, I have run into some weird problems on something like this.  The idle problem may be that the carbs are not returning to the idle position because of linkage stcking or the throttle cables to tight or a lean running condition. The back fire condition usually is oxygen getting into the exhaust gasses leaving the exhaust port. Either by a lean running condition or the seals between the pipe and head are leaking allowing air to enter the exhaust and exploding. I sounds maybe like the carbs need to be gone through again and then resynced and the linkages all checked out. Make sure there are no pin holes in the slide boot. Also once this is done put in a fresh set of plugs so it will be easier to read and locate a problem cylinder.