It helps with backfire as the standard iav isn't adjustable. From what I've read most people don't see to much difference with it but I haven't tried it so I can't really give you a good assessment. I'm sure someone will chime in that has it or has used it.
I had one on a Jackpot and it really helped with popping on that bike so I kept it when I traded it in for the XC and never felt a need to install it on the XC so far. Just didn't have the same problem the JP had. Contrary to popular belief; the steel frame bikes and the touring/bagger Vics are tuned and run different.
When I has my cams installed by Rylan i was gong to have it installed because I had a ton of popping with the ness honkers on my Vision with just the stage one download. Rylan said it would not be needed. He was correct. After he installed the cams and tuned the bike it has not popped in the 2000 miles since.
2013 Vision Touring. Shelbyville IL
Lloyds 116 big bore
Lloyds timing wheel set at plus 2
Lloyds adjustble intake
Lloyds HP cams
Lloyds quarter turn throttle
Ness Big Honkers
Lloyds Vision intake plate
Lloyds variable clutch
Heads worked over
Built and tuned by Rylan Vos at The Vic Shop
Installed one on my 08 Vegas. My intent was to improve the off idle throttle response (stalling) and reduce the popping and backfire. After quite a bit of fiddling (adjusting) it, my take on it is this - marginally effective. A slight improvement in the off idle throttle response, not much reduction in the popping and backfiring. You mileage may vary!
2008 Vegas 8-Ball Vic stage 1 pipes, laydown lic plate, Ness fly bars, led brake lights, front turn sig removed, Memphis Shades Demon windshield, Rivco signal mirrors,
timing wheel at +4