I bought a venturi pump off ebay for $20, my 5hp compressor set at 80psi keeps up with it no problem, run it for an hour, gauges reading 28". One thing I would add is if your system uses an R4 compressor, NEVER buy a rebuilt, my first one lasted 15 months, second one lasted 18 months, then started making horrible knocking noises. next one will be new.

Bob H.