Now you need your tune adjusted. Don't drive much, and avoid high rpm until that is done.

 

Yeah I was running a 406400 continental belt on my 3.4" griptec pulley WITH the additional idler pulley installed and after I installed the griptec I was still getting a bit of belt slip (I think, all I know is there was a TON of belt dust all through the engine bay after I suspected hearing some belt slip) so I moved down to a 395 belt, which was a pain to get on... but I still got a little belt slip with it until I tightened a tensioner a bit more.

Half of me thinks I'm getting slip on the crank pulley side but I dont have a way to really prove it and its minimal so, meh.

 

The 395 belt with the idler pulley is absolutely a pain to install. LoL. I got it but really had to fight. And then tightening the belt and checking for belt tension is a pain with everything installed.