Just an FYI, those tests are usually run in 'ideal' conditions with pre-modded cars.
'Ideal' means the test is done at sea level, in temperatures conducive to horsepower on an engine that just had the oil changed and is in pristine condition, and with huge fans blowing cool air right into the intake.
A lot of times, the horsepower claims are Deltas (changes from current horsepower). The initial HP could have been 500+ on a modified car, and then after the MAF install, you get a 512-515 reading. This is because the car already has a full exhaust system, intake, ported/polished, perhaps even blown. Horsepower gains are all relative to what has been done to the car.
So, legally speaking, yeah... they could have seen a 15 horsepower gain, but thats only with the other mods helping out. On a bone-stock C6, you'll get a crisper throttle response, probably 1 or 2mpg more, and maybe a couple of horsepower.
Bottom Line, the MAF upgrade is a good one if you have long term plans, but don't expect to install it right off the bat and drop a second off your quarter time
:thumbsup: