Ford Repair: fuel and intake, schraeder valve, filter package

Question
I have a 94 lightning, where is the switch to shut off fuel pressure so I can change the fuel filter, also do you think a k and n filter package is a good investment for my truck? Thank you for your time. Steve  

Answer
Steve-

  The isn't a switch, actually.  There's a small valve on your fuel rail (the long metal log looking thing over your injectors) called a schraeder valve.  It works on the same principle as a tire valve (also a Schraeder valve) but this one is loosened with a wrench.  Just remember to put a rag or something of the like over it so gas doesn't get all over the engine.  That will relieve the fuel system pressure.  As for the K&N filter package, it certainly won't hurt, just don't expect to get a huge difference.  Lightnings have a lot of hidden potential so I'm guessing you'd see maybe a 10-15hp gain.  Perhaps 20hp if you're lucky.  Remember...early Lightnings used Ford's marine application 351.  Swap in a new cam and intake...maybe some good heads and that thing will run like a scalded dog.  Hope this helps.

Steve