if you can hear the injectors you need a separator between the supply and return lines - me 94 blazer that i got from the original owner had a crate motor swap and someone left off the line separator and the constant racket drove me nuts - sounded like a fan was running when in fact it was the 2 lines rubbing together - after the separator it quieted down but was still able to hear it - i then split some 3/8 air line and slid over both lines securing them with some zip ties and now all is quiet
