Riding in cook city so 9 to 10ft. Silber supplied clutching, 2 1/2 to 3 gallons of AV
Okay. Few things...
1) Like I said, make sure your belt is in good shape. The clutching we provide is working well, and according to our infrared head gun, running at lower temperature compared to stock (pin weight really helps these clutches). However, clutches still get hot and belts can still glaze. Be certain this is not happening as its a surefire way to get slip. Even minimal slip can effect the way the motor is being loaded - especially at high RPM/WOT. Also remember, the RPM gauge may show 8000, but if the slip is quick and then the belt grabs again (hitting the rev limiter briefly) this too can cause exactly what you are talking about. Second suggestion - try a bit more pin weight and maybe a higher clicker setting (if you need to).
2) We obviously don't require you to regap plugs as part of the install. However, it certainly wouldn't hurt to gap them down slightly. This could be a sign that your spark is getting blown out (though in our testing we have not had this happen...)
3) make sure the wastgate is tight, hoses are hooked up, no leaks etc. A small boost leak can create these types of issues too.