Ok so I have 42.5's and a 2.8" pulley. Im only getting 12-13 psi of boost........

I have a K&N intake, GMPP cat back any answers would help!

 

are you tuned?

 

Your IDC must be ridiculous, I really do not recommend that small of pulley on 42's.

Joel

 

With a 2.8 you should be in the range of 15-18 i would say. You have a cat or not?

 

I have a cat, gm stage1 flash/tune and I replaced all vacuum lines. my gauge is the stock boost gauge. And no matter if I have the stock pulley 2.8 or 2.9 it still only reads about 12-13psi. As far as IDC's They are close to maxed but they are not the problem Im sure. Please HELP!

 

Check your boost bypass solenoid.

Also, check that you installed your new vacuum lines correctly.

 

How do I check the solenoid? Im pretty sure thats the black wastegate looking thing.

 

Correct.

Look up the boost by pass mod. It will explain what you need to do. It sounds like you are bleeding or leaking boost. Have you had the blower off recently? Was the gasket in good shape?

 

wow stop telling this dood to do all this crazy ****. you have a stage 1 reflash, when you put on the smaller pulley without the gm2 reflash your BOOST BYPASS SOLENOID is going to bleed the psi and KEEP IT at stock boost level. your car is fine and the pcm is doing its job. get a reflash from zzp or whoever you choose and everything will be fine. the bypass is there to prevent over-boosting. you should really be running a 2.9 on 42's at the MAX. 2.8 is giving those injectors one hell of a ride.

 

I never said they were the problem, but just letting you know that your playing a game with those.

Edit: Chevycobaltss beat me to it.

Joel

 

Yeah about 2 months ago. It looked fine to me. My gauge is kind of "sticky"too. its not real linear when it moves its like jerking.

 

Wrong.

The GMS1/GMS2 tune does not bleed/reduce boost like the stock tune.

The bypass is not for preventing over-boost. Ohh boy.

By the way doing the boost by pass mod is not "crazy ****" it is to check to see if his solenoid is working properly. It is only used as a test.

 

I ran a 2.9 and the gauge was still only reading 12-13psi so your saying I need a gm2 flash and it will bring my boost up?

 

ok the gm1 reflashes the pcm for a smaller pulley. your totally right

 

The GMS1 & GMS2 tune is the same.

You said you have the GMS1 reflash.

 

it doesnt matter what pulley you throw on, the pcm is still thinking there is a stock pulley and wont let it boost past 12.5, you can try the boost bypass mod im just saying ur wasting ur time with it because you will boost higher then stock when u bypass it.

 

Trust me. GMS1/GMS2 are the same exact flashes/files. You should know this by now.

This is not correct.

I had GMS1 back in the day. I upgraded to GMS2, and all they did was install the hub, pulley, and belt. The flash was left the same because its the same flash. Once again the GMS1/GMS2 reflash does not reduce boost like the stock tune.

 

OP, like i said check you vac lines and look for any leaks or problems with the boost by pass solenoid.

 

I read the boost bypass Mod does not affect boost at WOT? Just mid throttle... Im so confused how will the "BBM" get me the boost im looking for either with the 2.9 or the 2.8 ?

 

Question.

Why did you replace all your vac lines? Were they in bad shape?

I've never tried the boost by pass mod myself. I just know thats what many have used back in the day to check to see if the solenoid is working. I still say to look for any leaks and to check your vac lines.

 

I guess I didnt replace ALL the vacuum lines (my Bad) I replaced the ones going to the Boost bypass valve because yes they looked pretty "cracked" but it made ZERO difference.

 

So this boost issue was occuring before you replaced the vac lines as well?

 

yes. I replaced because they looked bad and I thought that was the problem for sure. but Im thinking thats not it.....

 

Hmm....

Do you remember what your boost used to be at before you noticed this problem? You are positive all your lines are hooked up correctly?

 

+1 for GM Stg 1 and 2 tunes being identical