O.K. there is a diaphram thingy mounted on the firewall behind the carb. It's about 4" round and has a chain going to the carburator linkage. Another hose has rubbed a hole in it and trying to figure out what it is and if it's needed. It has a small hose comming off the back going around to another box thingy mounted on the drivers side inner fender. Looks like when the linkage is depressed all the way it pulls out on the diaphram. Sorry for the description but I have no clue what this is. Oh yea 1975 F-250 4x4 360ci

 

That is the diaphragm for the cruise control, most likely.

Jason