Ditching the Huge Exhaust Housing

[adam 32]

ive got a t04e with a 1.06 exhaust housing, which means full boost is at 4500rpm. a little laggy for street use...

its making good power (271.6hp on an RB20) but its all top-end

my current setup also uses an HKS external wastegate and exhaust manifold. my questions are

A) how hard would it be to swap exhaust housings?

B) approx cost? (i would trade in my 1.06)

C) would i need to change oil/water lines? dump pipe?

D) which housing would u recommend, 0.60? 0.80? 0.86?