I went for the Milltek DP and sports cat (200 cell) and then mated that to a supersprint cat-back with a slight custom-made reducer (from 3" to 2.75 i think)

Whole system cost about £680 i think.

A cat-back won't do IMO - you'll still be restricted by standard cat/dp.

If my car boosted to 28psi i think i'd refuse to drive it until it was sorted. I am panicking about my 22/23psi peaks i see on mine - 28 sounds rediculous

EDIT - isn't 28psi something like 1.8/1.9 bar??? I know of 500-600bhp cars that run far less than that!
 
I know about the boost being to high, and in previous posts i have mentioned about higher bhp cars with less boost.

OK might just stick with a complete milltek system then.