Here is a list of what we determined by process of elimination....

-Tune: You have the GMS1/GMS2 reflash (does not pull boost like stock tune). Good there.
-Vacuum leakes: You checked, and found nothing. Good there.
-Boost bypass solenoid: No cel's, and performed bypass mod. Nothing changed. Good there.

The only thing left would be the boost bypass actuator.

Now let me ask you this.... Are you still running the stock exhaust manifold? (I know you have the production downpipe installed). I ask, because if you ran an aftermarket header, downpipe and exhaust your boost would be lower (due to less back pressure/restriction). Lots of things affect boost like temp, climate, elevation, modifications etc. A 2.8" pullied car with the stock exhaust manifold will more than likely see 16-17psi of boost on average.

 

Truth

 

Hey man....

I've been trying to help the OP with his boost issue. Have any thoughts on the matter?

 

Yes Stock Intake manifold stock DP with stock converter. all I have is a GMPP cat back and a K&N intake.

stock header aswell

 

Ok. Just checking.

I say pick up the actuator, and go from there. It's only $30 or so. Let me know how you make out.

 

if you ever figure this out, please shoot me a pm too! having the EXACT same problem.

 

So I just went out and started my car and was watching the actuator while i had a buddy rev it up. Its definitely moving when he revs it so could it just not be moving far enough? To make it even more interesting I was going down the highway and just when I hit the rev limiter in 2nd (7k) it like poped to 15psi then I let out of it.......

 

check your boost bypass valve. youll have to pull the blower off to do so. Once you mentioned the popping up to 15 i had a similar incident a few weeks ago. Take the blower off, and youll see a circular hole with a flap behind where the blower exits into the lower intake manifold. spray that with carb cleaner and work the flap open and shut at the same time. That could be closing, but not fully. You would still see the arm moving like mine did, i wanted to dismiss the issue till we actually pulled the blower off and you could see it moving but not fully closing.

 

Yep.

It's like a little throttle plate. The boost bypass actuator opens and closes it. I'm sure over time build up of blow-by would clog it up, and make it stick.

OP, this could be something to check as well before you buy a new actuator. You will need to remove the blower though.

 

Its not hard really. Or time consuming as long as you know what your doing.

Basically remove belt, disconnect intake, unplug throttlebody ( can leave attached to blower )
we removed the injectors. not sure if you have to do that or not to get it out but we did it, and unbolt four bolts on blower. literally takes 10 mins tops. 30 if your taking your time first time around probably if that

 

Nope. No need to remove the injectors if you are removing the blower.

The only thing that sucks when removing the blower is dealing with the tensioner!! I always uses a small pry bar instead of the 15mm open end wrench method.

 

This^^^^^

 

Finally something I can help you guys with!!!!!! The tensioner is the easiest part!!! On the tensioner pulley there is a plastic cover. You pop it off with a small flat screwdriver. One you get that off the is a a bolt that takes a T50 torx bit. Use the bit on a longer rachet and slowly relax the tensioner by pushing on the rachet handle towards the back of the engine compartment!!!!

 

Oh really now ? Ima have to try this out tonight after work bc the tensioner is the biggest PITA

 

I just use a prybar

 

Thats what I use as well. I don't plan on taking my blower off anytime soon, but I may invest in the pulley boys tensioner tool in the future.

I thought about doing this before, but didnt want to possibly crack the plastic cover.

 

alright so..... I took my car out to my dads garage last night to pull the blower off and check out the boost bypass actuator and possibly clean it. On the way there I got on this long country road.... So I decided to do a 0-100 pull and see what my boost was doing. 1st gear only about 5-8psi 2nd gear 10-12psi and 3rd goes up to 12psi really quick then slowly creeps 15psi just before I hit 100mph. So im curious if im just not seeing 16-17psi because it only has the stage 1 flash/tune?

 

I promise its so easy a caveman could do it! Ive been doing it this way ever since I saw this video on you tube just search "cobalt ss belt"

 

Like I've said before....

The GMS1 flash is the same flash that is included with GMS2. So with a smaller pulley (like you have) you will see increased boost.

To make you feel better....

When I first purchased my car back in 07' I had the GMS1 kit installed. Well, that got boring over time, and I had the dealer upgrade me to GMS2. All they did was install the pulley, hub, and shorter belt. The flash/tune was left alone. When I was GMS2, and still had the stock exhaust I used to see around 15psi of boost on average. Although, there are a lot of factors that can alter boost, and make my boost numbers compared to your boost numbers almost irrelevant. It still will give you a general idea though.

 

^ truth. again lol

 

Op. Did u ever take your blower off to see what was going on?

 

I did not. Im planning on it but I am seeing 15psi in wot in third gear and I guess with cat back and Intake its about right although I wish I was seeing 16-17psi with my 2.8" . Im going to take it and have my blower looked at tonight because it has been making a little noise for awhile. Its got 82k on it so it prolly needs a coupler,oil change and rotor bearings. I guess I never really thought about it to much but thats prolly why im not getting max boost....

 

Making 16-17psi on a 2.8 does not mean you will be making more power than a 2.8 car making 15psi. It all depends on if your car is running correctly right now.

By the way an intake does not lower boost. Exhaust modifications take car of that. A catback will not lower boost all that much. I still suggest you take a look at your blower, and bypass actuator.

 

So I took everything apart last night and wow... From the throttle body back it was so dirty in there it was ridiculous! But as for the actuator.. I shined a light through the open throttle body and could see light pouring through one side of the actuator valve but it was pretty clean. There is a set screw that I adjusted to allow the valve to close to were I couldn't see light anymore. Put it all Back together and by George I think we've got it! I went out for a test drive to see how she'd do on the a quick Highway pull. I got about 16-17psi Wot Third gear at about 110mph before hitting the Rev limiter. And Im am pretty pleased with that.

I guess my next question is should I be running the one step colder plugs? I have just the stock ones that I replaced about 3 months ago.

 

ill try it tonight.