Hi Steve and welcome, sorry can't help with feedback on GAD but only ever hear good or even great things about acid @ MSL they are based in Birmingham so maybe worth the travelling involved to get the best of the best.
let us know how you get on, its something I'm planning for mine when funds allow and acid will defy be doing it
Join Date: Jun 2002
Location: Staines innit
Car: W168, W169 & S202
Posts: 9,688
GAD tuning banned - Circumventing the rules is not good internet etiquette and it will get you nowhere.
I've just has my c320cdi mapped by PCS and would definitely recommend them. I actually had a previous map removed and replaced with theirs to sort some running issues. You wont be disappointed with the guys at PCS.