88 gmc van 6.2 diesel
I changed my system to 134
Rebuilt compressor
New accumulator
At idle compressor works good and cold
Soon as I rev up compressor squeals
Anybody have any suggestion

Check the belt. Even if it is a serpentine one with a spring tensioner, it may be dirty or old andweak and not tight enough. If you were running it before low on Freon, it may be taking more power to run the compressor now.

Thanks
I'll tighten the belt and let you know