Has started missing and running rough till I get up to around 60 MPH. I replaced plugs and wires had it serviced and lubed. I also replaced air filter but no improvement. Had the folks at Auto Zone put code reader on it twice and and got a reading that #2 & 5 cyls are misfiring and running lean. Problem started after a fill up of gas. this is a 4.2 V-6 with automatic tranny