UIM fitting?
 

Me: I'll remember what the major fittings on the UIM go to so i don't need to take a photo of this one

My brain: LOLOLOLOL he is so gullible!

What does the large nipple on the left in the photo go to?

https://cimg6.ibsrv.net/gimg/www.rx7...d7da223c89.jpg

Goes to the brake booster vacuum port/nipple. In OEM config, theres a rubber line that then goes to a hard line mounted to the firewall, then a rubber line with a one way valve in it to the brake booster.

thanks JP3!

I kind of remembered that it was capped but now can't find the cap (and I bagged and tagged all the parts I removed just a couple weekends ago!).

That would explain it - I have an AP Racing setup with no servo.

Will get a new cap.

Thanks!