I like it; it was exactly what I was hoping it would be. A very slight rumble at idle; enough to know it's there, but not obtrusive. At part throttle/cruise it all but goes away. No drone whatsoever. Mash on the throttle and it comes alive. It gets quite louder, but still not offensive. I talk on the phone a lot while driving and needed something that sounded meaner, without being too loud. The other systems touted on this board seem to be on the loud side; the Flowmaster is definitely on the quieter end. Another nice feature is it has a muffler and a resonator (gets rid of droning while cruising). It is a 2 to 1 system, but goes into a 3.5" pipe (what's stock, anyone?) which seems plenty large. It seems a given that a catback alone isn't going to give any large HP #'s, so I wasn't concerned about maximum flow. Just thought I'd share my experiences with the board.

Colby

To get most of the hp benefit, a cold air intake would help.

I have the Magnaflow then added the Volant Cold Air Intake. DEFINATE feeling of improved hp. I can't keep my foot off the gas pedal

Went form 11.9mpg to around 10

It definately feels alot more responsive and WHO CARES about the mileage, that's not why I bought an H2

Colby, I assume it's not the American Thunder version???

Actually it does say "American Thunder" on the instructions. Educate me, what is the "American Thunder" line?

Colby

P.S. Isn't the stock intake "cold air"? And isn't the common consensus that the stock airbox flows plenty of air? I wasn't going to upgrade the intake because I thought there was no real benefit.

From what I know there are two catbacks systems from Flowmaster for the H2, the American Thunder version uses a 50 series muffler (I think) and is the loudest of the two.

By your description it seems that even the American Tunder version is somewhat mellow in tone? I would have thought it to be loud...very loud.

Yes, this is the 50 series muffler. It was surprisingly mellow; borderline too mellow. I can talk on the OnStar phone while cruising and the party on the other line can't hear the exhaust.

Colby

I have the extremeflow cat system with cold air intake. Very loud and keeps you off the gas when on the speaker phone. For the hp and growl I think this one is hard to beat.

Is this a cat back or replacement muffler? what would replacing the muffler alone do?