Belt Slip

hey fellas
Recently installed Revan 13-6 kit and after first track outting my best was 12.4 at 126 mph, well I noticed the front of the supercharger to have black residue and automatically asked myself if I was getting belt slip, I was wondering what you guys with this kit are running for belt slip, are y'all running auxiliary pulleys, I have stock upper and 10% lower, any input would be appreciated thanks

I suggest either a 90mm idler or a shorter belt.

When I bought the 13-6 kit, I got the smaller upper pulley (2.396) and it came with the 90mm idler. Also got the blue gates belts. I too had belt slip and had black residue all over the supercharger. I bought the Auxiliary Idler Kit from van and that has fixed my slippage issue. Figured that was the cheaper option than replacing the tensioner, but was willing to do both if there was still belt slippage.

This is the one I purchased: http://www.revanracing.com/products/auxiliary-idler-kit-with-double-bearing-idler-pulley.html