Outer Limits 4x4 Board

This has probably been covered before but I am still trying to decide on how best to power up my '99 S2 Manual Disco TD5. I really only want to spend a few hundred dollars to get more power and torque and a few people have mention Bruce Davis chips plus some others. Anyone have any recomendations? I'm pretty sure I will have to get this fitted by someone who knows what they are doing but how easy is something like this to fit and how many variables are there for me to screw up if I try myself? I'm posting this on a few other furums as well incase you see this again.
I'm leaning towards the Bruce Davis chip but can't find any info on the net for them. Appreciate everyone's input.

Bruce Davis Performance Landy’s Pty Limited 233 Annangrove Road Annangrove NSW (02) 9679 1978

There was a review of these chips in 4wd montlhly recently....Nov issue I think

Cheers,

Martin