If it's been cleaned, and all that beautiful slime has been removed it's going to need to break in again. Is the pump or just the spray injection that's load?
I'm running an urchin pro without any mod's and it's quite just a takes a few weeks.
Maybe just through a towel over it to muffle the noise
the pump is fine, its the spray injection, thats producing a loud hissing sound. And yes I cleaned it with a water/viniger solution previous to using on tank
a towel under the spray nozzle? doesn't that just block the water flow? What you should try is taking a piece of plastic or laminated cardboard or somthing and placing it over the small box section where the injector is. and the putting the collection cup back in place. this will act as a muffler blocking the hissing noise from escaping
Dude, I told you to do the laminated corrugated cardboard mod. Put a piece nice & flush over the spray nozzle. Will be really quiet & won't sog up like a paper towel.
It worked out perfect, I covered the box over the area where the injector sprays (making all the racket). I shaped a piece of tinfoil that was folded a few times to to make it fairly thick and sturdy but making sure it didnt interfere with the spray injection but rather just muffled the sound.
I observed that it didnt mess with skimming ability and reduced noise greatly.