Ours is so old, I have no idea what brand it is, we picked it up used in '92. Replaced the motor and pump along the way, Grainger stuff, and yes, the nozzle is damned important. If not matched up correctly, it will back up (think "banana in the tailpipe" from Beverly Hills Cop). We've also had maybe four guns for it, also from Grainger. The point being, good parts make a good PW; I'm not the handiest guy around, but once I figured it out, it was a lot less expensive in the long run; it's been 7 or 8 years since the last repair...
Steve