I went to the track the other day and did 4 passes down the drag strip. The car ran good and I didn't notice any problems. After wards I was driving home and stepped on it and noticed my car was only spooling 10 pounds of boost. I have a 17% pulley reduction DDM cold air intake and an exhaust. My car always runs 15pounds of boost. I don't know where my 5 pounds of boost went lol. I have ruled out engine problems with a leak down test all 4 cyl were under 10% leakage. I have also ruled out the gauge being faulty . It is a new automated gauge that has been reading fine. I hooked up a known good gauge and also hooked up a fuel pressure gauge they both said 10pounds. I am not sure what else to check . 5 pounds is alot to lose. Any ides would be great. The car is an 03 MCS with 80,000 miles.

 

check all your lines, and maybe your bypass valve is open slightly leaking boost.

 

I know I don't have a vaccum leak for sure. But I ordered a Detroit tuned bypass valve. I'm going to see if that fixes the problem or not. But I was wondering if it would be that my belt is slipping at high rpms. Is that a possibility?

 

Yes...
you can usually hear a squeal if it is bad....
But I was at a dyno day, and Jan of RMW looked at the graph, and could tell a belt was slipping BEFORE it was bad enough to squeal...
General rule I think....
New belt yearly with a 17%
every 2 years with a 15%
and always use the right belt...a stock JCW belt COULD be used for a pulled car...they were used early on in modding, but better options are available...when a belt as long as the stock or JCW one stretches JUST a BIT...they start to slip very fast!
It is EASY to ZIP tie the bypass valve shut to test if the bypass valve is faulty....but you are getting a new one...so just wait for it and install it once IMO.

 

Have you looked at your SC boots?!
They rubber tends to get harder as they age.....then they can leak and split. New ones are about $75-80 from Waymotorworks.....
Look for oil seepage around the boots...this is one time that the PCV gasses that condense in the IC is useful....

 

Are you talking about the two rubber boots that go onto the intercooler? Or is there some other component that im not seeing ?

 

Yup...those rubber things on the end of the IC.

 

I'll look at them I had them off not to long ago to hook up the boost gauge and they looked and seemed to be in hood shape.

 

Just got done putting the DT bypass valve in. There was no change in boost it is still only spooling 10 pounds . Any other ideas? I'm running out. I think I am going to buy a belt tensioner and a new belt.