I can comment on the seal. Anything you modify can be used to refuse warranty. Not necessarily legal or rightly, but there are no rules as far as triumph is concerned and they will use any excuse to refuse IF they feel they are right in ding so. In other words, they might refuse you and ok another guy's bike with the seal removed.
That said, removing the seal made no difference on my stock 1600. Once i got the 1700 kit installed and TORs and UNI filter it makes quite a difference. If you want to try it, note that the airbox top ring that it comes out of is 2 pieces and you can pop it apart and pull the seal off and then put it back if you need to take it to the dealer and are worried about it.