Is there any other ECU I can use that will work on my car (06 MT car)? I understand I'll have to get the key reprogrammed.
I can fins a crap ton of AT ECU but IDK if they are different.

also I stumbled across a 2.3 Mazda6 MT ECU... what about mazda3 units?

**** the bigger picture is... I have this code, the car runs fine allllll the time. when I go to clear it is shuts the engine off. the CEL never goes off because if.
at one point rain water got in the ECU 2years ago so I'm guessing that had something to do with it.
-code p2610 internal engine off timer performance.

 

There are a few ECU that could work but all USED ECU need to be health checked and the proper operating program uploaded to work in your MADZA.
Check for suppliers of "recondition" ECU on the internet. Find one that actually has a brick-and-mortar address and that has been around at least a decade or more.
Yes, your DTC would affect a few operating system in your MAZDA and your diagnosis may be correct. I am surprised you are still able to drive the car without other engine drivability issues??