Can it be done? Why certainly it can. ECU tuning is allowed in ST classes as long as the stock computer case remains unmodified as well as any wire harnesses. Enter the below prototype. I'm probably counting my chickens before they hatch, but what the heck.
The adaptor fits inside the stock ECU housing as does the MS. However, the MS does require a small bit of trimming. The design of the board allows the MegaSquirt to use the Miata's VAM in place of the MAP sensor. Everything so far is bench tested and working properly with a MS plugged in. I just need to finish assembling the MS board that will be used in tuning.
The adaptor fits inside the stock ECU housing as does the MS. However, the MS does require a small bit of trimming. The design of the board allows the MegaSquirt to use the Miata's VAM in place of the MAP sensor. Everything so far is bench tested and working properly with a MS plugged in. I just need to finish assembling the MS board that will be used in tuning.