FI and timing are totally different systems. they can be built to "assist" each other but don't need to.
check out www.SDSEFI.com
for a bunch of EFI info.
you do NOT need an o2 sensor for EFI.
you can run a EFI with as little as a throttle position sensor(TPS)
it is quite helpful if you have a MAP or a MAF. (two different ways to sense load)
I have recently completed a fuel injection system for a 2443cc SCAT(similar to a VW) utilizing the SDS 3-F system. I hand fabricated the intake manifold. It works great!
if you are going to stay with big 3 EFI equipment leave it on the motor it came with. if the motor you are 'playing' with had mods or never came with EFI go with a turn key solution(Holley projection or similar) or if you want to get creative and have the patience to learn to program a system go with the SDS or if you have a lot of money ho with the MOTEC system.
If you have any questions let me know!
360 2v, 400 QT with low
33x12.50 BFG KO's
Thorley headers, 3" exhaust
Infiniti power leather seats