The best option is always a custom tuned Ecu. I believe I done a back to back test of Spoon Ecu vs Custom tuned obd1 Ecu some time ago, can't remember if I posted in on here or not - will try locate it.
A higher static compression will yield more HP per PSI of boost than the lower CR engine. If you are in the UK and plan to use the likes of Shell V power(99 octane) then for sure build the motor to 10.0:1 CR.
We tune Link Ecu's on all different kind of cars weekly, very good Ecu's.
Your 550cc injectors will be good as maxed out at 400bhp so best to upgrade. I suggest you go with Bosch EV14 style injectors, i.e Grams 750cc, ID725 etc...
I am certainly not as active as I once used to be on here, or any other forum for that matter. Unfortunately work tends to consume most my time nowadays. Nice to see some old user names that I recognize still posting on here.