I can't say how much. But it's a forgone conclusion that it will be higher than before. The Z guys use a resonated X pipe to reduce drone after hfcs and test pipes. I've mostly read about Borla TD, HKS and HKS clone users doing this. But at least these guys can justify it a bit more as these systems don't have a X pipe to begin with. (borla has none and the HKS/clone only have a H pipe.)

A different rear might be a better solution if noise reduction is what you want.

I have the Gen 2 Stillen Sedan exhaust. I don't think its too loud.

In fact, i kind of wish i had the Gen 1 since i don't think its loud enough.

I'm having same problem of tad bit too loud exhaust, myself.
Anybody know where I can get a cheap x-pipe or short resonator (both 2.5" diameter)?

You can get a polished resonated magnaflow x-pipe from performancepeddler.com for $95 shipped. If you don't the polished finish, it's even cheaper.

It will only get louder with the HFC

I'm not sure if this will work but I've heard they have been doing this for years. Try this:

aaaah funk it....LOL it was a pict of a banana in a tail pipe!

Sorry I had too.... LOL

uhh? fail at image post. banana in tailpipe

Damn, my last post would be so much better if the dang pict would show... FAIL! SMH

[QUOTE=TwilightBlue;4793650]I wonder how bad the drone will be once my HFC's are installed...[/QUOTE
Do you think you could post some sound clips once you install the HFC's because I've been wanting to do that for a while but dont know how it would sound with the stillen exhaust Thanks