arcing spark plug wire??

i have a grand prix (3.4) that i just replaced a bad coil on,one leg was bad causing a miss on that cylinder,a few days later the car started to idle rough,not stalling out or getting a "check engine light"but the engine in going from it's 2000 rpm to fluctuating up and down from it to around 500 rpm,seems like it wants to stall but picks up,a few years back i had a simular problem except the engine would surge up and down till warmed up,(wound up being upper intake gaskets)but this problem is the same hot or cold like a bad vaccum leak,i noticed today that one of the spark plug wires is acring on one of the coil legs,even though there doesn't seem to be a miss when it's arcing could this be causing the problem and seeming to be like a vaccum leak??