Quote Originally Posted by Scotty
I doubt that you'd need to disclose changing gearing to your insurance company
Any modifications from standard should be notified. If you come out of a bend on a wet road, grab the throttle, and the extra 'punch' causes you to crash.... well you can see how that will end up when you try to claim, or someone claims against you.

It's up to you though. There was a debate about tyres in a previous thread which was a bit silly as you can't actually buy the 'exact' tyres now that were available 10 years ago, but a mod that improved acceleration should def be disclosed.