The 225 bhp twin turbo conversion is fairly easy to do. I got a complete engine and kit for £650. It involved swopping the heads, drilling the sump and a few minor electrical mods. The only thing I'd say is get a vented bonnet as it really gets very hot underneath the standard bonnet.

Anything aboe 225 bhp then you need to uprate the clutch, pistons and I think a few other things.

If you get a kit I've got the t.t. installation manual somewhere that I can e mail you.

Cheers

Steve