i have 08 ss 5 speed and round 7k the boost fell off it used to go to 18-19 lbs now maybe 15 topps dealer says its ok they have a call in to gm plus i have a noise on first start up like moan/groning sound maybe like an internal vacum leak thanks for any help John

 

If youre tuned you should see about 20psi and if not about 15 is normal

 

no tune it had 18-19 up untill 7000 miles

 

My 08 auto felt the same way. I am now seeing 9-10 but only right as it shifts it takes forever to build boost. It has 11,500 miles

 

May be a silly question, but what was the temperature at the time? The engine limits the boost in colder temperatures to keep it at a constant torque rating of around 250 for the sticks 230ish for the autos.

Was -20c here the other day (-4f to you) and i was only seeing a max on the gauge of between 60 and 80kpa (damn Canadian gauge is in kpa, its around 9 - 11.5psi). Whereas in the summer i was peaking between 100 and 120kpa (15 and 17psi).

 

Yep, at colder temps you will see lower boost, but not less power.

 

72f

 

I hit 23 yesterday and the temp was high 30's......

 

This helps....I too noticed tonight that my gauge was at -60kpas while driving at 2000rpm and would only max out to 80kpas on full throttle. It was -14 celsius here and I was wondering the same. Damn kpa's, why can't everything be set in one system, it's not like we are fighting over the land or the Queen anymore. Can't we all just get along and put everything in psi. LOL.