Hi Neil;
I know it's tempting to cut a corner and use a carb to get flying faster/cheaper, but I'd really try to stay with EFI. Many advantages. I know you get screwed on shipping from across the pond which can make it hard to swallow.
Here's a really half-baked, out of the box idea, that you could look into that would save you a lot of money, take up all your remaining time, but give you a ton of satisfaction. Arduino micro-controllers. I'm just starting to get into them while I'm building my own data-logger for my first generation EM2 and am absolutely amazed at some of the ideas people have used them for. It's difficult to stay focused on my current objective and not stray down the garden path by getting distracted by all the things that can be done with them. Almost anything you can think of, someone has done with an Arduino.
They are an open-source hardware platform so there are many cheap clones available, with accessory shields for an almost unlimited number of gadgets. There are open-source libraries of code available for almost any conceivable project and I know in my browsing that I have seen some for engine ignition/injection.
You can even pair up several (or more) micro-controllers for redundancy. There are great you-tube tutorials to get you started and I recommend you start right at the beginning. I know just enough to jump right in, but there were enough things to trip me up that I finally went to the beginning and started learning from scratch to fill in the gaps in my knowledge and now this project is beginning to come together.
In most cases you don't need to wright your own code from scratch as you can find libraries with other users code that you can modify to suit your own needs. It's not as crazy as it might sound and id I didn't already have EC2 powering my plane, then I would probably attempt to make my own.
Todd
C-FSTB
13Bturbo 9.5 hours last week