Take it off to install the nozzles, it's basically sound deadening, to keep the engine noise down. Then you get the next big surprise, a nice chunk of metal right where the nozzles get screwed in. So, you gotta get a drill and make yourself a nice hole there to take the old ones out, and put the new ones in. I was gonna do this, and then decided that i was really lazy. I have a pair of green washer nozzles, if you know anyone that wants them let me know, i wanna get rid of them. Anyways, lets us know how it goes.