I just installed my megasquirt pnp2 on my 97 miata and ive come across some issues i can't seem to find answers for.
I am not currently running a wide band 02 nor a IAT sensor - everything is stock with the engine and the harness.

My installation steps i followed:
vacuum line coming from spare vacuum nipple right after the throttle body going to the megasquirt with no kinks
install megasquirt and load base map that i got from MegaSquirtPNP by DIYAutoTune.com (MS2E v3.3.1a MSPNP2-MM9697 file)
I set the 02 sensor to narrow band due to no wide band sensor which is default.
i then calibrated my TPS and set my timing to a fixed table then to 10 degrees.
I went to start the car and the car simply will not start without throttle input.
When throttle is applied to keep engine running, the engine does not like to rev and it runs very rough. I'm thinking it's a fueling issue but i am not sure on the flexibility of changing such thing without a wide band sensor.

If there is another thread with the exact same problem with a fix please link it here but I was unable to find one.

Thanks

 

You should probably get an IAT sensor and a wideband

 

This.

It won't run without them.

 

I had a similar issue on a '96. I haven't entirely been able to resolve it but I did get from not starting to running rough.

Make sure the injector settings in tuner studio are correct. If not, you may not have enough fuel for idle or too much and can flood the engine. I used the settings found on trubokitty. Carpassion channel on YouTube was also helpful for this.

Make sure the megasquirt is fully plugged in. A lose connection can cause misfires.

Set your timing with a timing light according to the megasquirt directions. If your timing is sufficiently off, it might idle rough. Carpassion has a good video on this.

I did those things and the car still ran like ****. Took it to a mechanic who found that the megasquirt wasn't firing injector #2, thus causing a misfire. Put the stock ECU back in and it runs like a dream. Contacted DIYAUTOTUNE about the misfire and they checked it out under warranty but couldn't find anything wrong. I haven't had time to try again.

Hope that helps.