I find it very strange why your wanting to go from 280 bhp straight to 400/450, obviously your already not 100% on these cars as you wouldnt be asking the question so why not just go for a decent stg3 set up, my car was 260bhp when i just got it, now i`d say its a genuine 330/350 and i can tell you the differance is very large, you going from 280 to 450 is not needed, but everyone to them selves an all that, good luck whatever you do and mind and keep us posted on the outcome