In that case, I believe you likely could use ECMLink after having the board socketed.
I have not heard of FuelTech, but more and more people/companies are turning up, as the market grows to find news ways to control the early Mitsu ECU's and their codings.
If you socket the ECU, then an Eprom chip could be burned to match your new hardware changes.
There is a guy that can burn chips with reliable code, that also has the permission from Jeff Oberholtzer to work on the original program language that was developed and sold under the DSMChips.com banner. Alternatively, you have to go standalone chip interface link ECMLink and use either a MAF or speed density setup.
There is however one other setup that is emerging, and that is SwedeDensity. Kaxlon.com and he is a member here too. Very interesting self tune setup he is developing.
You have options ....