my setup; Gt3582 with .63 rear +supporting mods+ pfc.
Boost at 3200, full boost at 4500ish.
I like it, even works well on tight 2nd gear corners.
Response is important but not crucial, afterall it IS a drift car your after and u dont drift at 2900rpm. Im happy with the lag, considering I usually use 5000+rpms.
If your still in the ''i need response uleh i drift at 30kms in 5th gear, so i need BOOOST'' mindset, consider this.
A mate is also putting on a gt3582 on his SR20 drift car.. a bit of perspective for u