I haven't had much time to work on my 175 but I did get the injectors our and head off. Three of the injectors had a bunch of soot on them and one was clean as a whistle! When I pulled the head the three cylinders were sooty and dry and the one was wet with fuel and a little beat up like something had gotten in the cylinder at one time. The head a cylinder looked fine but the piston was a little beat up. I think the piston was from an old injury someone put back together but would this clean injector be dumping fuel in the cylinder and causing the knock? Thanks for you thoughts or advice