i have had my 2009 HHR, 2.2 auto, for 2 years. i pull it behind my motor home. it is a great vehicle. i got 20 mpg around town and 29 /30 on the highway. a few weeks ago i decided to try to up the power and mpg, the exhaust is 2inch to the end of the cat, and 1 3/4 inch back and included a resonator and muffler. i had a local shop take it off and make a 2 inch cat back system with only a turbo (quiet type ) muffler. the whole thing cost 180.00 . i then bought and installed an Air Raid cold air system. the net result was i am now getting 22/ town and 35 on the highway.. with more power. the only time i hear more noise is when i floor it and the intake makes more noise. i don't get any exhaust drone noise

 

Glad it worked for you.
I had a magnaflow muffler put on my chevy express van and it made no difference in fuel economy, and I have a drone so bad that I have to spend another 140 bucks to have a resonator installed post muffler.
Not happy at all. I should have just had the factory muffler replaced with an oem one.

 

So you eliminated the resonator on the exhaust that is it? And the air raid..

 

ye, the resonator in the center of the car is gone. i put the turbo muffler is at the back with a chrome tip.. no drone noise at all. i just took a trip of about 250 miles with at at 70 or less in the back roads. i got 34.5 mpg big difference, for an automatic.

 

oh yea, the air raid unit is great. i originally got a system from bling light. it was a nightmare. but the did let me return it