Eastcoast Racing. Got one for my Xantia-same engine.
£370 though.
Benefits are you can fit it yourself in ten minutes.
Can move it to other cars (with same engine characteristics).
Adds 27bhp with no loss of economy (unless you use it for more grinability
all the time).
Highly recommended. Basically it overfuels the injectors more than the
standard settings would allow.
Other companies require the car to be left with them while they play with
the ems and fuelling. Bit worrying.
DaveK.

STAY AWAY from it stay WELL AWAY!

if yoiu want the extra horses go to a proper cartunig centre.
there is more involved than keeping the injectors longer open ( what a
box does by putting capacitors in between the fuel rail)
you have to redo the whole fuel maping.

Go to Ebay and do a search for HDI tuning.

I have not seen any claims for 125 bhp for an HDI 90 though, 115 seems more
common. If you try to take it higher, then the engine management will cut
the engine. They work on increasing the pressure in the rail.

They're great, BUT, use a specialist !

http://www.vanaaken.com/europe/index.asp or
http://www.allardturbosport.co.uk/ are the folks to see. They've been doing
this for years - I wouldn't trust my engine with a random company :)

Thanks everyone for replying , i will get it done from a specialist
Cheers