Ok guys, i am about to put exhaust on my 07 f250 cc and am going to do either a 4" or 5" turbo back system with no cat and no muffler. I called my local ford store today and asked about what kind of exhaust would void my warranty. They said that it must have atleast a muffler on (which i could put on to go to the shop) and said anything larger than 4" causes promlems with the motor. He said it causes the check engine light to come on, and doesnt have good backpressure for it, is this true? I would like to run a 5" tb but if i have to i will run a 4", what is yalls input on what i can run without voiding the warranty?