LT1 A/C Compressor Replacement

[mpramsey]

My current daily driver is a 1996 Impala SS and my future LS1 Powered 280Z sits on stands in my garage! The 96 Impala SS A/C compressor started making bearing related noises recently and I replaced it this past weekend. I purchased a remanufactured unit and upon reinstallation followed the manufacturers recommendation on adding oil to the new compressor. I added 3 ounces of PAG 150 recommended for GM compressors. I drained no oil from the old compressor yet the instructions indicated to add 3 ounces of oil even if none was removed from the old system. So I started to charge the system (no vacuum pulled) with a refill kit and the compressor progressed from cycling on/off to just staying on. Watching the guage as the pressure builds the compressor or belt starts to squeal at around 35 - 40 psig. I can only get marginal cooling effect. Is this an oil related issue as there may be too much in the system now. Or is it as simple as a worn belt. I suspect I need to pull a vacuum on the system and start the refill from an empty system. Thanks.