hi,,, can somebody tell me how to check and see if my egr is working right,,,,i am getting a bad pinging,,,also what is a good way to clean the egr system in case it is blocked,,,i am also getting a code 21 which is the 02 sensor and i can not figure it out ,,i am thinking that the egr might have something to do with it because of exhaust gases,,,the truck is running rich ,,you can smell the fuel and see a little black smoke,,,,the truck is a 93 toyota with a 22re