I got Ol Blue's Magnaflow and I did notice a bit of an increase in seat of the pants, but mostly due to the fact that I have the 2.2L and I swapped on the 2.4 cat back which was a larger diameter. The resonator is longer on the 2.4 also and that helped keep the tinny raspy ricer sound out of it too. it has a nice low rumble at idle, nice gurgle and pops when you coast, and you can keep the stock tip which I think is hard to beat in the looks dept. I still have it on there and get tons of compliments on it.

 

Post up a video of that setup Joepappa1, let's hear that

 

I found a cheap way to get good sound out of my hhr by just cutting the muffler off, and installing approx. 12-18" steel tubing and then adding a chrome tip. It looks stock, but sounds expensive. :)

 

I will once I get that damn leak sorted out! LOL Sounds horrible now. I'm gonna try a stock gasket next and hope that works. Ive also knocked out the cats since then and that REALLY woke her up!!!! She sounds really nice and throaty.

 

Here it is. slapped the original gasket in there, and got a vid of how she sounds. Hope this link works.

http://vid253.photobucket.com/albums...psatwcngyn.mp4

 

From what I could here it sounds great!

 

that sounded kewl only took me a year to response lol

 

So I am brand new to this forum. I found a very handy calculator for determining the best Exhaust diameter based on perceived/ measured HP. I think this would be most helpful if you were adding a turbo to a non turbo engine or a cold air intake to a naturally aspirated engine. If you know the predicted HP jump from either this calculator can take a VERY educated guess as to what Diameter tubing you need throughout the system from tip to tail.
Exhaust Size Calculator