ljefferson

I was wondering if I could get some direction on where to go to next with my 2004 F150. Since I ran a tank of 93 octane gas in my truck, I have been hearing this "chatter" It really only makes the noise as it is pulling up a hill. I have noticed that my gas mileage has suffered from this as well. I am not really sure if it is a matter of an exhaust leak or something more serious. Any suggestions would be greatly appreciated.