you can hear the turbo a bit more with the K&N setup. i bought it used for like $200.

a very good friend of mine who is a very good tuner lives in Miami, i can put you in contact with him when you're ready to get a tune. the HPTuners software cost between $400 (Standard Version) and $600 (Pro Version) and then it's another $100 to unlock your car's computer. BUT to have my friend tune you it'll cost the $100 to unlock the car and then whatever he costs for his time, i can get a definite price for you later today.

i personally don't own the HPTuners software. one of my best friends does and he tuned me.

 

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if the HHR SS is bone stock....... it doesn't matter what/how many bolt-ons you do to it, once that learndown feature kicks in it'll go back to stock power.

with a GMTU you'll experience gains with bolt-ons but not as much as you'd get if you were custom tuned with HPTuners or Trifecta.

typically a free flowing turbo back exhaust will gain you between 14-20hp because you're opening it up. the biggest gain with the exhaust on the LNF cars is the downpipe. the stock catback 2.75" diameter.