There are a few who say no but I cannot believe that the same mods wouldn't help the 06. I put my stock airbox back on just for giggles and I found that on normal surfaces (some rolling hills and flat roads) the mpg were the same or slightly lower (could be wind, heavy foot, etc) but I went Hill country this weekend and found that STOCK SUCKS!. What with mods I can do in 5th not floored I had to do in 4th and floored with a sad result. So I say give it a whirl the most it will cost you is $25 for a filter and if it doesn't work no biggie if it does WooHoo.
Clif

Traded for above-Custom intake, 2 1/4" ehaust w/Hedman Pack (pn 25005)

Awesome! I don't care what the nay-sayers say the proof is in the pudding.
Clif

Traded for above-Custom intake, 2 1/4" ehaust w/Hedman Pack (pn 25005)

Congratulations! Until you've done it no one can nay say is my opinion

2 1/4 in exhaust
Exhaust Pix
Intake and CC Breather

I didn't read all twenty pages of this post, but I'll let you in on something. There was a dyno/decibelmeter test done on about 30 performance mufflers. I remember two, the borla XS and Hooker Aerochamber, they were among the few quietest and least restrictive. Summit racing sells mandrel bent exhaust if one wanted to piece together their own exhaust. Honestly, the car is almost silent, there has to be some gain to be had from freeing up that restriction. Personally, I wouldn't go to 2.25 inch, I would go smaller and with smoother bends. I've never been a fan of glasspacks, I put them on a vehicle in H.S. and it sounded like a lot of the fart cans you hear today.

Just looked at www.summitracing.net
they carry
1.5
1.625
1.75
2.0
2.125
2.25 & up
all mandrel bent tubing in straight and various radius bends

I honestly don't think you'll like the sound you get from a straight through muffler like the glass pack or those magnaflows.

Thing is you cannot see the muffler so the way it looks is not relevant, I say give it a try worse case is you have to buy/try another.
Clif

Traded for above-Custom intake, 2 1/4" ehaust w/Hedman Pack (pn 25005)

Can someone please post instructions and part #'s (Spectre / K&N?) for the conical filter mod for the 2005 HCH-I's? I am planning to run to Pep-Boys or Autozone this afternoon and pick up the parts.
From what I've heard, the stock airbox is 3 bolts, and then I need a 3/8" hose and clamp to run back into the conical filter from the engine?

Thanks