Orright, for starters, the GTiR engine is a seperate SR20, and has very different internals to other sr20's.
Secondly, if you are forking out only $1500-ish for a quad-throttle setup, the $1400 for an aftermarket ECU is not so bad, cos if you ever wnat to go further with your mods, the ability to easily retune is already there, instead of getting it re-chipped over and over to cope with each mod.
Instead of porting and polishing the SOHC head, has anyone researched the feasability of the DOHC KA24 head from the Aussie spec U13? Many Nissan heads are interchangeable. It could be an easy budget mod, as DOHC always gives greater volumetric efficiency and a higher rev capacity.