EFI Nosie Hissing

[Fishheads]

Hey Guys , I have a 2004 RK with 14766 miles on her she runs great but I noticed a small hissing sound coming from under the tank some wheres, it seem to come & go. I traced it down I think it into the EFI system, I have allways heard this noise since it was new when I would turn the on off & on knob on the console it would hiss for abut 5 sec till it primed the injectors & then sstop. I think this part was normal but now I here it erratically while the motor is runing it seems to get a bit louder then softer sound kind of a rattle hissing sound. Ater the motor is stop it makes this same erratic hissing noise for about 7 sec, Is this the EFI pump or a vacuum leak of some sort. If is going out how diffucault it this to replace or repair the EFI pump....... Thank Glen