Ive been changing evap rubber fittings for the last 2 weeks or so, havent beat the code yet. Last one may be under the truck. Can someone tell me what the black box is that is medial to the driver side rear tire, and also what it does. I have a vague idea that it deals with fuel vapors.

 

That would be the vapor canister. If you can get someone to do a smoke test for you that is the best way to find those small evap leaks.

 

The line between the vapor canister and fuel tank is pretty rusted, what would I use to replace it? It looks identical to hard brake line to me.

 

Buy some bulk brake line of the same diameter. It usually comes in 15 or 25 foot rolls.