Not something I've done to my GTD yet, but something I've done FOR my GTD.... Ordered a DTUK stage 2 box. Should be here tomorrow then I can update this post to say it's something I've done
Put it/leave it on 4+1, unless you have overfuelling issues (I haven't, but someone (can't remember who) thinks they did and Andrew got them to put theirs down to 4+0. Maybe theirs is a one-off, or maybe using Millers with mine has stopped me having the same summer issues. You might get a regen very soon after putting it on (I did), but I have a regen about once every 800 miles now. You're in for a treat.