Pre-Turbo Question

[rb20_au]

Hi guys,

I have been reading through alot of topics in here and have a few questions i couldn't work out the answers for,

I'm currently running a Nissan RB20DET Motor with a T4 turbo running around 18-22psi with a intercooler(warmer) but with alot of lag, which i would like to relive myself of.
I'm just wondering what size jet i would need to suit my application? and when would you start it injecting (what boost?), i'm using a cheap turbo for which i have a replacement here so that's no concern, also how far back in the intake pipe should the injector be situated? The pipe is probably around 40cm long at the moment, Have a SHUREFLO (sp?) 100psi pump and wiring/valves.

Main problem is a little bit of detonation up past the 19psi mark and little mid range power due to laggy turbo.

Any advise would be good.

Thanks.