I think AMD are doing 10% discounts or free fitting on exhausts anyway at the moment:
http://www.amdessex.com/products.variant.cfm?variantid=370
If you are not on stage 2 already have you considered getting the discount on stage 2 and getting the exhaust fitting with the group buy?
I'm on Bluefin and to get their stage 2 would cost only £50 so I I was to go ahead that's be the way I'd go. Their posted gains aren't as much as others remaps but I will ask if they're conservative figures. At the end of the day £50 is ****** all compared to paying to get stage 2 from someone else and paying to get their stage 1 too.