finally found time to throw in my Hyperflow - ?? (Yes, I STFA)
 

I don't recall anyone specifically commenting on this but I assume its normal to hear a brief "Chhh" sound when you hit the gas? Almost like a mini blow off valve type of sound? I noticed it when I was reving the engine in the garage. I'll post more on my thoughts later but quick summary is:

-Noticable difference in throttle response (worth the $$ for this alone IMO)
-Car "feels" a little bit faster
-Sound with non-res cat back is mean
-Install was easy but having trouble getting the trim covers to fit perfectly (yes, I made sure the air box bumpers were removed). The CAD divider seems to sit a bit high which makes the covers sit a bit high.

Normal. You hear it when you got WOT and close abruptly; basically pumping the pedal.

I Would go and check... But wait i CANT....(sorry just very bitter) GRRR

The brighter side of the story is you're at home and not in jail ;-)

Wait till you see the throttle response with downpipes installed :)

Make sure that the heat shield is properly seated below, sometimes it wants to hang ...
 

when your installing it. Once flush with the bottom of the chassis, you should be good to go. But then again, you want to allow for a "seal" between the heat shield and the hood.