I just returned from a 2000 mile road trip (two up) to New England (Americade - Lake George, NY; and Bike Week, Laconia, NH) from northern Virginia. Earlier this year I installed the Cobra PowerPro, along with the Thunder Air Kit, on my 2011 ABS Voyager (I left the factory exhausts in place). I was expecting more performance and better mpg then the 38 mpg I was getting. Here's want I observed:
Based on my not so scientific butt meter, there was a felt increase in performance, in nearly every gear. Twisting the throttle in the lower gears will get you to speed in a hurry; however, there is a price to be paid in reduced mpg. Dropping into 4th gear to pass while on the highway is confidently fast while 5th remained the main highway gear until you hit the flat blacktop and you want to cruise at 70-80 mph.
During the trip my mpg ranged from 35 - 41 mpg. Perhaps it is stating the obvious, but given the increase in performance I had to change my throttle technique to maximize mpg. It was so easy to get to speed in a hurry, without even giving it a second thought, so smooth and early shifting got me better mpg (duh). The bike was very responsive, so when working it aggressively through the twisty's in the NH mountains or in the stop and go traffic of Wash DC, mpg was 35/36. At highway speed, 55-65 mph, it would get 40/41. Above 65mph, it didn't matter whether I was in 5th or 6th, mpg was in the 38mpg range (the same as before the installation).
I run full synthetic oil in the bike which helped reduce felt heat on my inner thighs. The engine temp gauge was usually pointed straight up at the halfway mark or below while on the highway; and in stop and go traffic, just slightly above the first mark right of halfway.
With the addition of the Thunder Air Kit, there is a little more noise coming up from the engine, but it isn't bothersome at all. There is some backfiring/popping upon hard deceleration upon down shifting; however, it isn't something that bothers me or my spouse.
When all is said and done, I'm getting more performance with about the same mpg. If I behave myself, I get better mpg, which I couldn't get before the PowerPro/Thunder Air Kit installation. I'm keen to believe that each bike will perform differently based on road conditions and rider technique. These were my observations. Ride safe.