used eflex for 2+ years and 45k km's now in my VE2. With the odd 98 tank thrown in when out of Sydney.
On 98 octane I get 12.5L/100 avg speed 55kph
on eflex 15.2L/100 same speed. So you fill up a bit more, but the $$$ savings are there.
Take note this is with a Tuned ECM. I Have a Xcal3, so I can flip between "stock" map, tuned 98 and Tuned E85. I'm lucky that I have 3 Eflex servo's within close distance of me.
It's great stuff if it's available to you.