I have a 1988 38 ft. conv. with 671's rated for 485 HP. During a survey there was one bad injector on each engine so prior owner had all injectors replaced. It originally had M110 injectors and they were replaced with 7255's per Detroit. The boat used to be able to get 2400 RPM WOT with the old injectors. Now I cant get past 2000 RPM and cant get up plane. Rack is adjusted properly, linkage and cable move all the way, and I dont think there are any fuel restrictions. At 2000 RPM it does not blow any black smoke and there is more movement left throttles in the before it hits the stops. Any ideas?