For a couple weeks now my truck has been misfiring but not setting off any CELs. The spark plugs only have 10,000 miles on them, but the motor does have 167,000 on it, I rack them on. Anyways, well finally I through a code of P0303 which is a cylinder 3 misfire code. What steps and in what order should I try to fix this? I'm thinking coil and plug, and fuel injector cleaner first. Any others?