Oddball stuff

I have a 2009 hhr ss auto, 140k. Stock car. When i first got it and romped on it i was seeing 10psi in first then 15psi in second. About a week in the car it started feeling sluggish. Soon noticed im only getting 6 1/2 -7 psi. Under normal driving and short bursts of get up and go its fine. Anything more it'll fall on its face. Maybe 2psi tops. Netural and a restart back to that 7psi. Not a full limp mode i can rev all the way up but no go.15-20 minutes of driving itll pop up a engine light. P0299 every single time. Read around and most commonly linked to the waste gate. Ive adjusted with it, checked it make sure it was fine. Nothing i did made any impact on how it made boost. Vacuum hoses seem good, change out vaccum solenoids top and bottom. New ac delco iridium plugs, new upper charge pipe and intake pipe. Haven't done the lower pipe that runs into the intake manifold itself from the intercooler. Checked the bypass valve too. No cracks or anything. Even ran fuel additives to help clean out any gunk in it. Mpg's have improved and i average about 25 in town more and average 27 or so cruising around at 50-55 constantly. It does however occasionally flash the o2 sensor and the cat icon on my little scanner. Could that have anything to do with it while not throwing a code for it? What boost it does make it spools up quick. I did check my impeller on the turbo when i did the intake pipe for any play. There was the slightest bit but nothing to be concerned over.
The people that i purchased the car from didnt exactly treat it the best either. In fact hardly did anything at all to the poor thing. What i have done to it the car itself runs better as a whole. I dont even burn off any oil hardly, not enough to add any oil over 3k miles. Every once in a blue moon it cold starts rough for a second then clears up and purrs. Other than a alternator belt squeaking some and the tensioner pully starting to rattle it sounds very healthy. I really like the car and I want to fix it up right. Im just about out of ideas and patience. Its about to go to a chevy dealer soon for engine diagnostics if i dont figure it out soon. Ive now owned it for about 4 months. Done just about everything that's needed to be done, fresh suspension, brakes. Down to the Alt belt deal this boost issue and a soon to be replaced busted sunroof assembly.
Any new insight is well welcomed and appreciated. Im well aware of the mileage and the possibility of a worn out turbo. Im not jumping to that conclusion til ive worn out all other possibilities. It doesn't smoke or smell like a bad turbo at all. It keeps that 7psi constantly. Its daily driven also. Other than a k&n drop in filter and a brake upgrade kit everything ive put on the car has been OEM even running the reccomended mobil one motor oil.
Appreciate and information, thank you.

donbrew

I can't read the wall of words. P0299 means to check for leaks in the intercooler ducting, the bypass solenoid and the wastegate solenoid and restricted exhaust.

whopper

https://wordcounter.net

Cat Man HHR

I guess you guys never took the Evelyn Woods speed reading course in grade school.
I got through that large paragraph without a problem and understood it completely.

Oddball stuff

Cant read? I apologize for my wall of words but i did say what i did already do if you did read through it all. Both new solenoids, intake pipe, upper charge pipe, spark plugs. Both checked to see if the wastegate was moving freely and both adjusted it and test drove between adjustments multiplie times with no differences. Between all of that done. Ran CRC guaranteed to pass through it a few times. Helps burn off carbon deposits through the exhaust. Gained 2mpg average but again no boost difference and still the same issue and engine code. I have not changed the intercooler pipe that runs into the intake manifold. But i have checked it multiple times had the car up on a lift, bumper, under shields and all removed and checked and poked around. I've checked most everything thats linked mainly to this particular code.

Only variables i see change is on my scanner when sometimes the 02 sensor icon is blinking and reading an issue. Could that just be linked to just the sensors misreading or both the cat and the sensors both being shot out?

whopper

It's just us old guys have a problem with our crappy eyes.

Cat Man HHR

And it's just an old guy asking the question. I use cheap dollar store reading glasses myself.

RJ_RS_SS_350

That was indeed challenging to read. Hitting the return key twice (frequently) would have broken a long post like that up nicely. Kudos to you for providing enough info, many times we have to ask the 20 questions. Also it wasn't just one long sentence.

Check to make sure your vacuum lines are routed correctly, FMG has a pic of the routing for the bypass solenoid.

I would really suspect that you have a vaccum leak(maybe the vaccum tank?) or a boost leak. There is a link somewhere for a homemade boost leak tester.

Oddball stuff

Again, my apologies for my lengthy description. Ill be more attentive to summing it up and better spacing. I did try to be detailed.. lol thanks for the inputs. I had it up in the air lastnight again and looked, mainly looking what i gotta get into to change my 02 sensors. I did check vaccum lines but that doesn't mean i missed something. Routing looks fine. Car as a whole hasnt been messed with too much. Will keep poking around. Ive narrowed it down at least to a boost leak of sorts or something with my 02 ssensors and or cat. Im gonna have to do a pressure test. Car is 10 years old now and 140k... something has to be dry.

Again thankyou guys. Anything is helpful from a different perspective

donbrew

Many have found a crack in the intercooler at the inlets and outlet.

Depends on if it doesn't boost at all or gets up to a point and drops.