Shop air dilemma

I have a huge (for a home compressor) 5hp 80 gallon upright, 2 stage, 4 cylinder pump, it's an Emglo brand. Had it for about 15 years now, and I do alot of blasting with it. While running my blast cabinet, it runs and runs and runs but holds ~90PSI while doing so. It is rated at almost 18CFM at 175 PSI. Its probably getting tired, may not quite put out the air it used to. but it is 220V single phase. I KNOW that Quincy and others sell a similar unit with single phase 220.