Recently after stopping at an off brand station for fuel, I experienced no boost, low power on my 2009 SS Stage 1. Figuring that I had just got a bad load of gas I was glad that I had only put in 4 gallons. I went ahead a put in a whole can of octane boost and filled the rest of the tank with known quality fuel. When that didn't fix the problem I was stumped. No time to go to the dealer as we were towing it down to Mexico in the morning. That night while trying to fall asleep I remembered I had a similar problem years ago on my 2002 GMC Envoy. The fix was simple, all I had to do was to make sure the gas cap was on tight. Sure enough that fixed the problem. If there is any silver lining in this cloud it's the fact that the engine seems to make more power with octane boost added. I can't verify this, it's a seat of the pants feel. In any case we made it down to Puerto Vallarta in Mexico, where my SS attracts crowds and comments all around town and is a pleasure to drive on the narrow winding roads outside of town. I LOVE MY HHR

 

Surprised you didn't get a "check engine" warning as that's what happened to my wife the 1st time she gassed up and didn't put the cap back on tightly.