Basically, its advised you get your mods done then go for your remap to get the best out of it.
But you can get it tweaked to suit mods after you get the mods done if you go for remap first. Although Mr Whippy said the map is auto adjusting so will adjust slightly to any mods, although as above for the best results you'd get it tweaked again. Exhaust wont gain you that much, especially compared to what you'd gain from the remap itself at first though.
Stage 1 can be anything from a completely standard car being remapped to being a remapped car with exhaust/intake mods.
But you can get it tweaked to suit mods after you get the mods done if you go for remap first. Although Mr Whippy said the map is auto adjusting so will adjust slightly to any mods, although as above for the best results you'd get it tweaked again. Exhaust wont gain you that much, especially compared to what you'd gain from the remap itself at first though.
Stage 1 can be anything from a completely standard car being remapped to being a remapped car with exhaust/intake mods.