Belt Slip! Help!

I got my car dynoed. The numbers were low (373rwhp 365rwtq) for my setup. (see signature) The car was only pulling 6# of boost at 6,000 rpm with a 3.25" pulley. I think that the belt is slipping bad. Alot of belt dust. I am running 113" Gaterback, but that is the size vortech recomends with a 3.6" pulley. I am wondering what size belt i should be using with a 3.25" pulley?
 
Damn thats way to long of a belt for a 3.2 pulley. I'm surprised it doesnt throw the belt off.

I was using Gates belts when i had my 6 rib setup and with the 3.6 pulley i used a xxx1080. When i went to a 3.2 pulley, i went with xxx1075. I think it tried the xxx1073 but it was too small.
 
Damn thats way to long of a belt for a 3.2 pulley. I'm surprised it doesnt throw the belt off.

I was using Gates belts when i had my 6 rib setup and with the 3.6 pulley i used a xxx1080. When i went to a 3.2 pulley, i went with xxx1075. I think it tried the xxx1073 but it was too small.

I believe that 99 and 02 have two different belt configurations. That is why your belt is so much smaller. I think I am going to try a 112" belt to see if that helps.
 
The boost number is too low. The horsepower is okay for that level of boost but I would confirm the boost gauges are working correctly also. Make sure you don't have some kind of vacuum leak.

I am sure the the boost gauge is correctly. I think to do not have a vacuum leak. If i did I think I would get a CEL and the car would run like crap, which it is not. I am getting a lot of belt dust and when I shift the hard it falls on its face. I am going to try a smaller belt. If it is not that It could be my bypass Valve.
 
Ignore my last post:

You could have bearings failing also in the blower. However, I had to replace 2 blow off valves because they were fluctating and wouldn't hold pressure. We moved my blowoff valve between the blower and the intake which necessitated a larger blowoff valve later to solve some of the problem of downshifting and the stall factor of the impeller blade when that happens, which causes belt wear.