how to clean fuel injector rail

[dagwood15t]

hi im new to forums but i have a 97 mercury mountaineer with 5.0 v8
i keep getting a p0308 code which is #8 miss fire
i have new spark plugs, wires, and distro blocks
so the only thing i can think it would be is the injector
how can i clean it with out removing the intake manifold
i have a mityvac system but don't know where to plug it in to the fuel rail
any help would be great
thanks lee

 

[Turdle]

The fuel supply and fuel return lines have connectors which are both in the front driver wheel well. You should be able to see them right next to each other near the upper control arm to frame bolts.

 

[dagwood15t]

do i disconnect both of them and then plug the return line or leave the return line on and run the cleaner threw the supply line with the fuel pump deactivated