I have a 2005 XJ8L. The only major options are nav and premium audio.

The first issue is an intermittent and sometimes very bad miss that occurs during a hot start after the car sits between 15 minutes and an hour. The dealer has pulled codes showing a miss on cylinders 1,2,3,4 and 5 but they can't reproduce the issue even though I can do it without trying.
They are replacing plugs and coils on 1,3, and 5. There was a baffle that was allowing oil into the low speed breather, that made a large difference but the miss still shows up. This is a very bad miss sometimes, think big block with a very lumpy cam. Shaking and banging. BAD!

My wife complained that the passenger seat felt loose so the dealer replaced the seat track, the new track has an additional motor for lower cushion depth, I found this by trying to adjust the seat angle and found that they had hooked up the extra motor instead (GRRRRRRR). The dealer is telling me that this part supercedes the factory part, can you verify? Can both front seats be retrofitted with the upgraded switch packs and can I expect full fuctionality?

Thanks guys.