Is there a convenient place to hook up a 3/16 ID hose to run to a pressure gauge? I'd prefer to use an existing port rather than drill & tap.

 

I went off a nipple that was un-used on the intake manifold. You can always tee off of any of the lines from the intake manifold. I routed the line through one of the plugs in the firewall, and mounted the gauge in a gutted eyeball vent. 20 minute install.

 

Pic From Flyin' Miata's Guide