here is a thought, just talk to the tech. The dealer i had do the install, had never done a hhr stage upgrade.
but i spoke to the service manager, and the tech (who does all their corvettes), and felt completely confident in their skills.

I have had 0 issues with the install

 

Does anyone out there have any dyno runs/stats with just the performance filter,Stage 1, and exhaust upgrade. I don't have any intercooler upgrades or any more than I just mentioned. I am looking to find out numbers that are happening around the world with the Stage 1 upgrade. I have had the Stage 1 for about nine months now. Havn't really got to put it on a machine. What is this Stage1 really doing for me? Numbers (HP's,torque,output whatever).

 

There are a couple of dyno postings just search... GCSD and Mightymouse have dyno's posted to their Sig's. there is also one posted on YouTube claiming 284hp to the wheels. The power seems to range from around 268 to around 305-310 with all the toys and stacked tunes. bear in mind that you lose a bit with an auto and the normal reduction between the crank and the wheels. Qtr Mile times with the add-ons are in the mid to low 13's(5sp LSD w/drag radials) to low 14's for an auto. Look up World's Fastest HHR on YT for a good run, eventhough he was asleep at the light