Hi Trevor,
We had a coil fail in a mate's T5 XC90 a few months ago. He used a spare S40 T5 coil I had until we could get a new set of coils and plugs from FCP. Replaced the lot because it came out at around $300 total.
The V8 coils are more expensive and there are more of them, of course. I've tended to be a bit wary of aftermarket coils particularly...pulling excessive current will burn out the drivers in the ECU and that's a far harder problem for me to solve. I tend to replace plugs more often than recommended - I figure it puts less stress on the coils as well - so far I've never had a coil fail yet.
(My automotive history is mostly 1970s British orphans - I'm used to replacing plugs and coils myself...)
Hence my (not actually so generous) offer. The previous owner bought 3 aftermarket coils which he didn't actually need, and gave them to me after the sale because he had no other use for them. I keep one in the car for emergency (I drive interstate fairly frequently) but as soon as one fails I'll throw in a genuine set. Therefore I'm unlikely to ever use the other 2 coils... and they're just taking up space.
