For the Evo I'd probably suggest Mark Shead too, or Simon Norris since both have produced a number of well known cars which produce the goods.

It seems funny that particular after market management seems to be favoured on certain makes of car, e.g:

Impreza's = Motec
Evo's = Autronic / Gems
Cossie's = Pectel

I presume it's just a case of what the particular tuner prefers working with.