Coil packs question

[Fun_Bucket]

Is there an average life span for the coil packs on a VP V6? I removed my plug leads one at a time from the coil pack while the engine was running, and the spark between 2 of the leads was a lot weaker than the rest. Is this a sign they could need replacing, or could it be something else causing it? Finally, looking on Ebay, it seems a full set of coil packs can be purchased used, with a 30 day warranty for around 50 bucks. Is that a resonable price? Some say they include a DFI module, can some one tell me please what that is?

[camstatic]

The DFI module is the unit underneath the 3 coils. As for the weak spark I'd be looking up what resistance you should be getting through the windings with an ohm meter.

[COMMY VP 666]

at repco, each coil is $50, so x3 - $150
and dfi about $100

[Peter89]

cheap coil packs may not be as good as stock, you'd be surprised what difference a decent set makes.