I am vacuuming my AC after reassembly and before I nitrogen purge it, using a HF 2 stage vacuum pump. My pump does not seem to want to reach a "full" vacuum (~30inHG), even with the manifold set disconnected from the car, relying on the quick connect seals. I've tried two manifold sets and they both agree. I tried changing the oil using fresh vacuum pump oil. I am getting to about 25inHg. I checked the local weather and we are at 30.12 inches pressure. Is this a normal reading or is it likely that my pump has failed? I have used this pump a few times before, and don't recall having any problems with getting the gauges bottomed out.
Sort of tempted to eat the cost and take it in to an indy to be filled on their machine. The local import shop is pretty pricey but there is a small shop that doesnt specialize and has pretty fair prices.

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'85 300D - federal spec, built in late 84. 85 300D Complete AC System Rebuild