Well, i don't think it is "completely blown out of proportion". Gas will expand to fill a space. So, a larger diameter exhaust will result in exhaust gases expanding to fill the area, and subsequently cooling faster as it spreads out. Cooler air is more dense, meaning too rapid a cooldown will rob you of volume expansion (gas expands when heated). Volume expansion is a driver in pushing exhaust gases out of your car as it moves toward the lower pressure found at the exhaust tips. So, a drop in expansion will slow the gases leaving the exhaust, robbing you of power low-end. It is not as much of a problem the higher you go on the RPM band because the gases are heated to a higher temperature, lessening the cooldown effect.
There is also a member on another thread on here who installed the GTM 3" exhaust (its not 2.75", but it gets the points across) as he plans to install a TT. He himself said he felt a little less power low-end.
I never said it wouldn't "make up for it at the top-end on the same premise". As I stated above, he will be fine the higher the rpm's.
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