zxr 400 help with restricting

[dale91192]

Hi all I've just brought myself a 2001 l9 zxr 400... Such a nice bike, I was wondering if anyone would know which restrictor kit is better for the bike at all?
I have the option to put either a 33bhp kit on or a 47bhp kit on, I dnt mind which I use but I wanted to know which one would prolong the life of the bike the most as I am planing on owning thes bike fir many years and wouldn't like to destroy or ruin the engine in any way.

Thanks all

Dale.