@NHXRUNNER, I copied this from my post in Tacomaworld. I am the one that makes these. It was something I just did for myself first then people wanted ready to install instead of fabricating their own.
People might be getting some belt slip and not realize it. It's not like you are building boost and then the belt slips dropping boost to 0. It's more intermittent and progressive than that.
The problem is we only have a 5 rib belt to grip an already small pulley at 3". This is with the correct belt wrap of 190° as guided by the idler pulleys. This give a total belt to sc pulley contact area of about 5".
Once you start going smaller with sc Pullies, you not only lose belt contact area from the smaller pulley alone but also due to the position of the non adjustable idler pullies.
Some info...at a constant 180° of belt wrap, pulley contact area is as follows:
3.0. pulley 4.71"
2.85 pulley 4.47"
2.7. Pulley 4.2"
2.5 pulley 3.9"
That is almost an inch less contact area on the 2.5 pulley vs the 3.0 and that is not taking into consideration the extra load (hp) required to drive the sc with the smaller pullies installed or that you get less belt wrap the smaller the pulley.
What the belt wrap mod does is restore some of the lost belt wrap which brings the belt to pulley contact surface area closer to stock.
Hope this clarifies and sorry if I'm cluttering your post XMPLRY808. Bad ass truck!