We have tuned a few of the 2.5i setups. Due to the poor 90 oct fuel we have adding more timing or leaning fuel out much yields very little. Shift timing is not a function of the ECU you would be programming with opensource. Remapping throttle plate control does help some in terms of response.
To really see gains with tuning your time would be best spent on supporting mods. Exhaust, intake, cams, water injection, etc. Nitrous is also an option, a 50 wet shot could be fun with a good tune behind it.