JJW-ND,
Was that estimation (280-340 HP) with the plate in stock (280), then fully forward (340) position or some other?
My '98 5spd with the #11 equivalent from Bully Dog Tech. (Stage 1, rated at 287HP) did 247 HP on a Mustang dyno last year. Only other mods were an Amsoil foam air filter, the TST elbow in the turbo line, and the AFC star wheel backed off some.
Since then I've added a few more (see sig. ). I'll be checking it again on the same dyno this weekend.
-Jay