I recently reinstalled my Cobalt gauges after deciding not to trade in my truck. Now I'm maxing out at 21-22 psi when before I'd top off at 28-29 psi. Any ideas what could be causing it? I went back and slapped on some pipe dope but no difference in psi. I'm currently on the 160 level for the PPE. I'm wanting to install my boost controller which has never been installed but want to figure out the changes in boost pressure. I talked to the guys at Autometer and guy said to add the pipe dope which has already been done. He also said one of the wires might be kinked but don't see that being a problem. Any suggestions would be appreciated.

did you replace the little brass fitting that compresses to make a air tight fit on the tube. I took mine off and reinstalled it with the original and found that it was leaking. 2000 rpms and a water bottle with dish soap should help.
Check your boost tube boot on the turbo to make sure its not slipping off.
check for maf code.

EGR bad?

Zeus, not sure what you're talking about, could you expand?

No codes thrown. EGR was been blocked for a while now. How would I know if the egr is bad? As mentioned, I took the gauge off, drove around for about a month, then put it back on. Just seems awkward to me....

Do you have the mechanical or electronic Cobalt boost gauge? If mechanical you have a 1/8" tube running from the intake to the gauge.

Electronic. Just three wires running into the cab. I might have an idea what it might be. One of the wires that goes into the plug into the actual gauge was a little loose before I installed it. Could I use a piece of foil or something else to make sure I'm getting a good contact?

Seems that might be the problem. Took the gauge apart to have a look and broke one of the metal ends on the wires. Need to call Autometer Monday and go the rest of the weekend without a boost gauge or boost controller...