What does the OEM "boost solenoid" connect to?
 

2001 miata

I currently have nothing connected to it (other than the wiring to it), so it had the one nipple open.

I have a flat top im, and have the evap canister removed. Running stock ecu

EGR.

Oh, so if I dont have an egr valve, this stays open to atmosphere?

That would appear to be what you described to us, yes.

The stock ecu doesnt use it as some reference measurement or something? I just want to make sure its correct to be atmo, or do i run a vacuum line to it off the intake manifold?

It uses it to check for correct function of EGR.

https://www.miataturbo.net/megasquir...bration-88492/ shows calibration for future use with MS if you wish to run baro correction, as you once spoke about.

And because I dont have the EGR setup nor the solenoid attached to it and the boost sensor, I'll always have a code tripping a CEL.

Thanks for posting that about the baro correction, good info if I ever go back to MS