Coils tend to either work or not. If you get a deterioration it'll be breakdown of the coil insulation, causing a short or some arcing. You would feel this as jerking or a misfire especially under load... and almost certainly the dashboard ignition light would flicker.
If your beast has lost a bit of its mojo.. then look at the more likely/cheaper things;
> When did you last have a new air filter? (Do you have a "sport" cone filter?)
> How old are the spark plugs and who last gapped them?
> Any intake leaks (check the airbox piping to the manifold is all "tight")?
> Whip off the inlet pipe attached to the manifold and clean out any oily gunge in there.
> Give the MAF sensor a squirt of electrical contact cleaner.
> Stick a whole bottle of injector cleaner in the tank, next time you fill it up.
If you're sure everything is as it should be, then you can start delving into the more unusual/trickier reasons it may be feeling lethargic.
Ralf S.
