I have a 2000 f250. V10. Randomly started running bad. Smokes. Smells of gas bad. Spitting fuel from rear passenger exhaust port. Code is p0172. What is likely causes?

 

P0172 is a code for Bank 1 too rich, meaning that you have too much fuel being delivered and not burned in Bank 1 of the engine. That seems consistent with fuel coming from the rear passenger exhaust port. I would suspect a fuel injector stuck open on the rear passenger cylinder which would just dump fuel into the cylinder any time the fuel pump is running. If you pull the spark plug on that cylinder, it is likely to be soaked with gasoline. Usually if the fuel is not being burned because of an issue with the spark, you will get a misfire code for that cylinder and you won't have so much fuel that it is coming out the exhaust port.