Ebgil

I own a 2011 F150 XLT. I put a Rancho Readylift 2'' leveling kit on it and went from 275/70/18 to Nitto trails at 295/70/18. Ive also put on a Roush exhaust which sounds sweet and a K&N cold air intake. What i'm confused about from reading so many forums and talking to friends is do i need to take my truck to ford or some off road performance store that can program the computer to read the right mileage and what not. Ive heard the cold air intake and exhaust have a factor in all this to. The dude behind the ford counter told me that a larger tire size wouldn't make much of a difference unless I went to 37's and wanted to charge me 150$ for an " attempt " at a reprogram of the 295 tire size. What do I need to do ?