I run about the same pressure and same grit. But like you some days take forever to clean a small item.
I tried pressure 60-85.
What I find is the pick up tube and where to feed hose goes into the gun get clogged.
Material is not old enough to be dirty but does seem to lump.
As Arizona is dry it is not moisture. so maybe static.
If I jam the pick up tube up and down and wiggle it some thing it clears and clean for 15 minutes or so, other days I need to keep wiggling it.
If that does not work then a quick disassemble of the gun tapping out the clumps and I am back running.
May I will bump up the pressure and try some of that speed abrasive mix.
I am starting to lean toward electroplate for the micro rust, keeping the blasting for paint.
