I have searched here and pressure washer forums. friend and I are sharing a 18" surface cleaner with two tips of unknown brand using our own Honda 13 HP with cat pump model 66DX40G1I 4000 psi @ 4 GPM. Right now it only runs at about 1800 psi. I have found a tip chart but was wondering what the user recommended tip size should be and what all around pressure I should shoot for? Can I put a 2.0 tips for 4000psi and turn down the regulator or rpm to lower the pressure. I have a pressure gauge that I use every time but the friend doesn't on his I am gonna set his up to match mine.