The probelm with our ECU is the Open Loop AND Closed Loop...most piggybacks work with one or the other...there are only a few that work with both...
Funny all my Ford EEC-IV's are the exact same way. I thought almost all ECU's were like that? I'd think the problem is the OBD-II, coding and amount of control that is built into them. They just don't allow for much modification.
