I had my truck running tonight and every time you stab the throttle it made this screeching sound. I think it was the belt slipping but I couldn't pinpoint it.

Would a couple drops of PB blaster cause the belt to slip? I was spraying the bolts on the turbo along with a few others (like the fuel filter mount) hoping that it might help get some of them loose when it comes time to pull the turbo (I've worked on old turbos before so I know how bad they get) and I think some of it may have missed its mark...

Should I put on some belt dressing or just let it work its way off?

 

If it is slipping the serpentine belt is: 1. too long 2. gone hard/shiney and cracked 3. the tensioner is not working correctly.

Belt dressing makes a mess........ just check the condition(s) and repair the problem.

 

if the problem came from the pb blaster it will dry out after running awhile.