I bet you that "detuned" iteration of the 3.0T is not THAT detuned.
I bet if you dyno it, the N55 and 3.0T make very similar power. The 3.0T in the S4 is said to be underrated and makes closer to 330whp. So all the detuned one would need to do is make 270-275whp to match the N55.
'98 M Roadster stg 2+ S/C @ 13psi(cracking 500hp this summer) +'13 EBII M Sport 328i 6mt BMS stg 1+