I need some thoughts on the 4008.

Best vac I've seen is 14 inches. It settled back the other day and held at 10 to 11. Today I arrived nothing's running... it's holding it 5 to 6. I walked the lines looking for leaks and could find nothing. I have two separate runs with independent shut offs. I shut both down and then watch the vacuum on those lines to see if they held with everything shut down and they maintained the small amount of vacuum in them for 10 minutes without leaking off. So I'm thinking that there's nothing wrong with the lines.

However, I also deadheaded the pump with a vac gauge in place and watched the vacuum and the best it ever pulled was about 8 in.

With the inlet port blocked off and vacuum pulled, I shut the pump down and watched the gauges for 10 minutes and again they maintain that for 10 minutes and there was no loss.

I'm starting to wonder if maybe I have a bad diaphragm in the pump. Are there adjustments to the pump like an aqua tech? I know there are set screws on the front face but I believe they're adjusting the cycling nature of the pump.