What Is This?! Whats It For?!

Im doing a Head Gasket on my 84 b2000, and I got everything unbolted except this damn thing! It connects all the way around the back of the motor, and T's off to the carb?! I literally climbed inside and had a jack handle over a crescent wrench(because I didnt have a wrench bigger that an 1") and all I was doing was stripping the nut. After literally snapping a crescent wrench completely in half I just decided to cut the tube about an inch away from the nut. Im uploading a picture of the line that goes to the header that I had to cut. The small red line is where I cut it with a body saw.(All done on my computers Paint Program lol) I figure its something for emissions? I noticed on the front of the header there are 2 of those, but they're cut about 1 1/2"-2" out from the nut and crimped. I would have just unbolted the carb and kept that line intact, but im not really fimular with Mazdas, or carbs because ive always owned chevys with TBI's. I plan on taking the Carburetor off eventually to clean it though because I just bought this truck and it has almost 300K on it. Im not complaining though because I picked it up for $200 from a co-worker that dailyed it, but it blew a head gasket and he recently got another vehicle so he just parked it and left it. All it needed was a head gasket and I was in need of a vehicle that gets good MPG! And ive always wanted a B series! Hope someone can help me out!!!

EGR tube?

Cap it off you will be fine.