What is the little device that sits between the secondary injectors? Small, looks like it has a vaccuum line going to it. Do I need it?

Picture would help. https://www.nopistons.com/forums/pub...DIR#>/wink.png

sub-zero cold start assist injector perhaps? It uses the same vacuum line as everything else but insead 90% antifreeze / 10% water goes through it when oil temp is below a certain point.

Just got my camera back. Picture is below. What should I do with this? Do I need it? No need for sub-zero start assistance in Texas, if that's what it is....

Ooops!!! Smaller pic....

Thats the cold start assist. Mazda issued a TSB recommending the removal of it. Basically, it dumps antifreeze into the intake if the temp is below a certain temp, but I fail to see how that helps the car...

Rip it off? Cap it? JB Weld? What is the best way?

You can cap it off, make a block off plate, or use JB weld. Ive had success with all of those at various times.

its called the doohickey i believe.