I bought both Stage 1&2 filters and a PC3 off Yilt on here.
Fitted them Saturday (well Yilt did - cheers mate

), first go today coming to work (weather has been appalling here!).
If anyone is thinking of doing the above then do it!
Big difference, much much better. So much smoother, no noticeable surging/jerking.
Too short a ride to estabilish if the extra couple of horses is noticeable, but so worth it.