Thanks for this, I appreciate it. I think the late model tanks are metal?
Anyhow that is my next course of action. I'm going to pull the tank and try to clean it out. I don't think I will use water though, probably will use something like acetone or laquer thinner. Depends on what I find tank material wise. Acetone can destroy some plastics in short order.
I was thining that there could be a sock filter of some kind.
Here's the odd thing. At startup when cold, the mechanical pump will make adequate pressure (I have a gage showing around 5 to 6 psi). Once its warm it drops a lot, down to the 2-3 psi range. Anyhow we'll see what I find once I drop the tank. I'll definitely take the opportunity to clean out all the lines and replace the hoses.