I have a 91 Liberty/Legacy GX AWD Auto 1st gen wagon, running on original ej22 boxer flat 4, currently on 187xxx kms. Mostly stock, well maintained, and rare to find in its condition. I live in Australia.
Also unsure of when eco-mode was introduced (Legacy introduced in 1989, and going by my 1991 which has eco-mode, narrows it down), though I can tell you you're looking at a reduction of 0.1L-0.3L fuel use over 100kms, which is definitely noticeable. If you're not going to be smashing the accelerator and braking hard.. this is awesome to have. Most of the time I drive in eco-mode, though sometimes I enjoy making use of the punchy lower-end torque for fun. Also keep in mind your air-con will suck back the fuel the higher it is set too.
Just keep doing your homework, and talk to enthusiasts/mechanics where possible. Hope you can lay your hands on something decent mate
