I have an 08 hhr ss on a normal I'm pushing 25 to 26 psi boost quickly and holding at that. But here in the past couple of days at any point time I can get on it full throttle and I will only hit 20 psi and hold until 4500 revs and then slowly hit 26 psi boost by red line. What could cause this and how do I fix it without spending a lot of money

 

25-26 is not normal boost numbers for a stock SS. You either have the GMTU or an aftermarket tune. Other possibility is an inaccurate boost gauge.

Until you "fill in the blanks" so to speak on what mods you have, then it's hard to just guess.
Also stating your mileage and what transmission you have would help.

 

Talk to the guy who tuned it.

 

I'm not sure what upgrades it's got I bought it about 2 months ago. It has 89k miles and it's a manual transmission. I know it's tuned 26 psi is not stock

 

Other than the tune everything else looks stock under the hood

 

My guess is that you have a slight boost leak?

 

If you're tuned to 25-26 psi on the stock KO4 turbo, get it DETUNED and run a max psi of 23-24 psi, especially if still on stock intercooler + piping. Beyond that the turbo's being overworked and is pushing heated air into the intake manifold.

Later
Allex

 

Ok I figured it out I have had it looked at and I have the trifecta tune and everytime I would get low boost I would have my cruise control button on mostly from my wife driving the car so basically when the cruise button is on it turns the tune off and it runs at 20 psi and with the cruise button off it runs at 25 psi

 

The best problem you could have lol. You can have the tune revised by trifecta if you don't like the way the car is running, or you upgrade parts. There is always HP tuners software as well.