My easy check for vaccum leaks is to use a propane bottle with an unlit torch head on it. Turn the gas on and point it at various places around the top of the engine while it is running. If there's a vac leak, the engine will suddenly run much better while the gas is getting sucked in.

Since you have to remove your plenum to replace the spark plug wires, you'll have a chance to be real close to a lot of vacuum leak potentials. One to check is the place in the plenum where the shaft is controlled by a vacuum actuator for the butterfly valves. I have a leaker right there in mine, and it's right up front so I found it rather easily. Naturally, I found it right after I put mine all back together, so I haven't fixed it yet.

John B.