i recently had tune up with plugs emission clean and fuel filter they also changed oil and did 27 point inspection. after getting truck back it warms up always before use.lol now when i travel too town 6.5 miles away, the thing rough idles in gear, when i back up it chugs and misses then when idleing in parking lot to find parking it feels all rough and missing. when on open road up too speed it runs fine. it has the 6.0 liter v8 this is a mystery. it ran fine when i took it in for annual tune up. why is this happening, disabled vet help please 