Probably late reply, but...
OEM ecu is robust item, if you dont want fancy features or not planing to change setup in near future.
Remote tuning(chipping) 20years old car+management can results as you mentioned. Its realy need to be done in person.
Aftermarket ecu, it realy doesnt matter for you, i would choose solution from most skilled/referenced person you thrust a most. Its more important. Then you can run megasquirt or pectel, depends on your vallet