if its hot out u will see less boost.. i got a 3" and i dont reach 15psi durin the day when its really hot, but when it cools off itll go to 15psi and sometimes even higher

 

Nothing like during the winter before roads get nasty and all that cold makes the cobalt run like a champ :.

 

hot air - less boost

EDIT: already mentioned above, sorry

I also have stage 2 and a 2.9", and my boost hits about 16-17 psi.

 

I have been running Nate's 2.9" for about 6 months now and i have never had an issue with it. I have also not experience one instance of belt slip.

 

I had one of nate's pulleys and was experiencing less boost also.I noticed that the ribs in nate's pulley are slightly thicker and not as deep as the GM pulley.Therefore it makes the belt ride higher, which would be like adding a slight increase in the size of the pulley.This was just my experience.Nate's pulleys are really nice.You may just have to get a slighlty smaller pulley to compensate for this.so if you want a 2.9 pulley you may want to order like a 2.88 or a 2.89.I have the GM stage 3 pulley which is 2.99 and I see about 16 lbs at redline.

 

Could it have anything to do with outside temperatures? I don't see full boost in my car when it's hot out like I do when it's cold...

 

i have the same thing happen, i installed 2.9" pulley and i only see 15.3 psi max on my aeroforce interceptor. Hitting redline it spikes to 16.5 for a millisecond, but thats it. I still feel a small increase from the stage 2.

 

you should see lower boost if you have anything done to your exhaust. header or dp.. i know b4 i installed my header and dp i was seeing 17.5 to 18 lbs on the 2.8 then when i installed the header and dp it went down to 15 .. but the car still pulls like it did when i was seein 18 lbs or so

 

Correct.

Also keep in mind that our ECMs have quite a few ways that they limit boost. Boost will be bled off in cases of knock retard, high AITs, etc. That's part of the reason you see people with the same mods getting different boost levels. A decent tuner can help with that. Also, any mods done that help the engine breath, post SC, will lower boost, but increase the actual airflow getting to and through the engine, increasing HP.