if you want safe 12 second passes in a WRX you will more than likely have to go with a bigger turbo. front mount should be your weapon of choice

 

I have a friend that put 297 whp down with a turbo xs top mount

 

get a TMIC and not to disrespect but for low 12's the APS 725 d/r is a bad choice. it's a huge fmic that requires much more air then other fmics and obviously tmics to compress so you'll be very laggy - would definitely need a shot. i'd recommend the aps tmic - i use it with a PE 1820 and a 35 shot. I can do 12.3's all day at CO altitude.
and btw i used to have an aps d/r 725 set up with aps turbine.. good for bigger blocks.. but low 12's and 350whp is about all you'll get out of a stock ej20 block.
-j.

EDIT: forgot to mention the APS TMIC for me runs daily 20-21 psi ecuteked and 350 whp no problem and a lil' more with that 35 shot!

 

so say i go with the turbo xs fmic what can i do to take care of the lag

 

smaller turbos produce less lag and less power a bigger obviously the opposite. My suggestion for you is to go with a tmic if you don't plan on doing more then 350 whp or low 12's. fmic if you plan to get into 11's. besides a tmic compresses quicker then an fmic due to the size - so less lag there. so look into 20g's or PE 1820 (i'd recommend the PE) for low 12's and a tmic. no need to spend more on something that you don't need. get a lil' shot of nos like 35 fogger though so it just chills the tmic and you'll be doing low 12's possibly a high 11 on how you drive but that would be pushing your stock ej20 to it's limit safely with ecutek or a good tune.