HHR SS missing hesitate when using tune
 

This just started a week ago, when i select the tune button it chugs pops then takes off as normal. Another issue is 50% of the time you step on it the boost stays low, then if you feather it up and down with the throttle it finally jumps up to 20lbs. Few times i got blow off valve error but most of the time no errors. With the tune off no problems.

Well. Then it sounds like you've got a tune issue. Nothing we can do to help you out.
Sounds like you need to contact your tuner or the vendor if you installed it yourself.

X2 and maybe loose wires, grounds and hose clamps on your charge pipes and IC hoses

Agree with FMG. What's the tune button? Little more information might help

Mine did stuff like this after my HG repair. It was the intake plumbing on the charged side. Look it over. I had both water ingestion and leak issues. Either can create this symptom. The engine is expecting more boost than it receives...

HHR SS misfire
 

I have an issue only when the Trifecta-Tune is engaged. when i floor it with the tune on it starts popping missing badly, not always, but most of the time now. If i move the accelerator back and forth i can sometimes get it to stop missing and go. Cant figure it out maybe the computer? i get an error on occasion when this happens of cylinder 4 misfires. I use to get error for the Turbo blowoff but i replaced it with a high quality one now the error is number 4 cylinder misfire. Keep in mind none of this happens with the tune off, even if i floor it. I re-programmed the ECU with the tune again to make sure it was not a data corruption issue.

Plugs, injectors, fuel pressure.

Loose coil or injector wires

DI injector seal also.

HHR SS Misfire
 

Ok i changed coils packs, injectors, checked for turbo leaks and i still have bad misfire above half throttle. Below half throttle runs fine. I have a fuel pressure gauge on the low side in the car that reads normal during acceleration> Im at a loss , ECU ? Ignition box ? Sometime error on cylinder 4 misfire. Valves look caked. But i really do not want to remove the exhaust manifold, turbo etc to do the walnut thing