all sounds good matt.
can't advise you on the turbo issues, but can on the injectors and mangement.
if i were in your position, i would go for 4 x large injectors for sure. there's little benefit in going for 8, but there's many potential problems (like only 1 out of 2 working, needing a second fuel rail, blah, blah)
stu at motorsport developments has done a lot of work in getting large injectors to work with a l8 ecu, and i would definitely recomend that route with clode loop fuelling for off boost. you will require a live map at that stage of tune also. you can also have a l8 modded to run a coil pack for a healthier spark than dizzy shit.
other management options would be P8, autronic or pectel or SECS S8 or other more obscure options like:
http://www.electromotive-inc.com/products/tec3.html
http://rptune.eu.org/
to spend all of that money on maching and parts, and then not do the fuelling correctly would be foolish imo. 'ladelling it in by the bucketload' is a recipe for disaster.
whatever management you choose, mapping it will be the most crucial part of the whole process
air injectors are just a method of boost control. personally, with your plans, i would go for a standalone boost controller that could be used either with integral or external wastegate turbo's.