Vapor Canister - Replace?
 

So my gas mileage has been poor lately, so I decided to find out why. After cleaning the air filter, I decided to pull the plugs to see if I could find out anything. Spark plugs 5, 7, 4, and 6 all had strong smell of fuel on them. Im thinking leaking injectors could be a possibility and I also read that maybe the vapor canister could make that strong gas smell also. How can check to see if the canister is operating correctly? If this is one of the problems, could it really lead to bad gas mileage considering its supposed to catch gas vapors when not running and not actually fuel? I want to test it if possible since I priced out a new canister and its 90 sum bucks. Thanks!!