Truck Repair: Engine miss, spark plug wires, intake manifold gasket

Question
I have a 95 Ford 4X4. The engine has had a miss for about 2 months.  I have had the fuel filter replaced and the PVC valve also.  I checked the spark plug wires and don't see anything wrong.  Should I replace them anyway?  Could the distributor cap be the problem?  I would appreciate any suggestion.  Thanks

Answer
Hi Duane,
I wouldn't just run out and buy a set of wires on a guess. There are many things that could cause a miss. And everything can be checked for.
A vacuum leak, like the EGR valve sticking, broken vacuum hose, intake manifold gasket, dirty fuel injector, dirty or worn spark plug or wire, low fuel pressure, bad injector.
Check the cheapest things first, like vacuum hoses and clean the EGR valve.
You should be able to pull the plug wires loose from the coil pack or distributor cap one at a time, and see which wire makes the least difference. Don't pull them off the spark plugs, or you may get a shock. Then swap that plug wire with a wire from a different cylinder, and see if the miss moved with the wire, which would indicate a wire problem, or if the miss stays at the same cylinder, in which case you should check that plug.
Good luck,
Van