I have noticed when I go to WOT from 20-25mph to alittle over 50mph then 0% throttle I hear this pretty loud screach, sometimes. Is this my belt sliping? I have the over sized idler pulley and a Gator back belt.




You can see some rubber on the pulley.


Ultra close up you can see the rubber alittle better.

I'd be more tempted to inspect your other idlers. Maybe lightly oil the bearings on each one and see if the problem goes away.