Ive reinstalled my engine after replacing my flex plate and have everything just about hooked up except for one line that for the life of me I cant remember where it went to. Any help is much appreciated.

 

It simply vents to the frame. The other end of that hose is likely flopping around loose inside the driver side frame rail. It's just a vent line for the charcoal canister (that larger black box), and that box stores the fuel vapors then burns them off when the engine is running.