im confused!!!! which megasquirt do u have because the megasquirt 2 has an internal 2.5 bar map sensor. tuning for exhaust temp isnt going to do u an good. to properly tune you need to tune based on engine load. you need to tune using tps, rpm, load(map sensor) and wideband o2.

 

i have the 2.5 and i am using tps.rpm map and wideband. But i know on others engines that the exhaust temps are used to give you a clue of what is happening in the cylinder. watching the temp can tell you if something is going wrong. I have not hooked up the sensors yet but the plan is to, not for tuning but for reference.