Join Date: Jul 2017
Location: Snohomish County, Washington State
Year/Make/Model: 2007 Kawasaki Vulcan 900 Classic LT
Color: Black & Silver
Well, obviously at this point your bike seems to be running WAY rich -- either too much gas, too little air, or both. Is there a difference between "popping around" and "backfiring?"
My experience suggests that v-twins in general tend to backfire if you snap off the throttle -- probably inherent in the design to a certain extent, and maybe from the cam design as well. A rich mixture will make it happen more, since it's more likely you'll have still-burning and unburned fuel/air mixture being dumped into the tailpipes and BANG. If your backfiring was excessive before the change, it suggests something was wrong before you dropped in the fuel control thing. Maybe they sent you a unit with the wrong setup for your bike, or maybe it's doing just what it's supposed to do but something's wacky in your FI system.
Obvious first steps would be checking the air supply system, especially air filter, and, of course, removing the Cobra unit and testing.
Any other mods on the bike, especially intake or exhaust? Is the FI light on?
"Don't force it. Get a bigger hammer."
- William Shakespeare