Okay I just bought my car last month and I think it has the performance upgrade already installed, how do I know for your what makes me think it does is that the gas tank cover says premium fuel there's alos a GM performance sticker under the hood and my car will boost any where from 18-20lbs if any of you guys could help me out with this or a sure fire way for me to find out would be awesome! Thank you!

 

Welcome to the site.

If it has the GMTU(GM Turbo Upgrade), the sticker in the gas tank door will say Premium Fuel Required. The factory non upgraded sticker says Premium Fuel Recommended

Also, with the GMTU, the Tmap sensors will be changed to the Bosch ones with the blue sticker on them. Here's a picture that shows the upper Bosch sensor. The lower one is not in the picture.
Having the stickers doesn't guarantee that the GMTU is installed(anyone could just stick them on)
but if you have the Bosch sensors, then it's a pretty sure thing the upgrade is done.
From the boost numbers you posted, sounds like you have either the GMTU or an aftermarket tune.

 

Okay awesome I'll will deffiantly check that out thank you for your help its greatly appreciated!