You would be better off pressure testing the system as well as vacuum testing. Your system may not leak under a vacuum, but under pressure it may. Under vacuum, the seals or O-rings will move in one direction and under pressure they will move in the other direction. This can and does happen. If you are able to, put a gauge on the low or high side port and then pressurize from the opposite port. Watch the gauge for 20-30 minutes to see if you have a pressure decay. That's my suggestion. It's based upon my experience as an engineer at one of the OEM manufacturers. In the recent past I spent several years working on the repair of HVAC systems on new units at the factory. We pressure tested all leakers with helium before evac'ing and refilling.
Just my 2 cents..............