My 04 with 141k miles ran just fine on the way to work. Zero problems. I have always had a steady check engine light on as there is a small crack in the gas tank gasket. has never been a problem.

When I went to drive home, it was about 16 degrees out. The truck started, but ran very rough all the way home. Code reader said misfires on #3, #5, #6 cylinders. Cold or warm the engine does the same thing. Figuring that many going wrong at once, the first logical stop for me was the coil pack. I replaced it, and it has made no difference. Heading out in 10 degrees to pull plugs and check wires, but I suspect something more.

Truck is stock except a K & N breather and a cat-back.

Any ideas would be welcome

First off, ditch the K&N, and I'd start with cleaning the MAF. More than likely it's soiled and can cause multiple misfires. Also check all normal maintenance items, such as plugs, wires, fuel filter. Someone also had strange cylinder misfire codes such as those and replacing the coil pack did nothing. Turns out it was the wiring connector to the coil pack. It had a loose wire coming out of the plug. Pushing them back in solved his problem. Check with a multimeter to make sure no wires are loosing contact.