mmm i don't think the RB25 is a slug, i've given a twin turbo manual soarer with 2 equivalent T28 twin turbo set up but complete stock car apart with 3 inch zorst and i kept up and i have FMIC and 2.5 inch zorst non tuned so yeah get it checkd out b4 spending big money mate cause the 25's aren't that slow ! haha ur case is abnormal matey ^^
Cheers
Chi