Megasquirt or standalone? You replace the entire stock ECU with a new ECU, no need for a chip then.
There are a lot of 323 GTX guys running standalone, and a lot of Aussie guys running various types of standalone. I've run MS on my capri when I was still running the 1.6 but do not have it installed now.
End result = capable of being tuned, can run any size injectors you want, very versatile.
MS has a pretty steep learning curve, if you build it yourself you'll want to have a pretty firm grasp of electronic circuits and soldering/assembly. The tuning can also be a bit tricky you DEFINATELY need wideband.
Here's a decent guideline:
Power goals
Under 200-250 HP - Chipped ECU
Over 250 HP - Standalone.