I remember a guy on here months ago that was pulling his hair out over what ended up being no spark to one cylinder. Turned out that one of the brand new plug wires he just installed was bad right out of the box. It was actually sort of funny to me because when he brought it back to the parts store (I think it was Autobone) he said he got in a fight with the guy at the counter over it, almost a fist-fight, lol. Now that's frustrated!

Soooo, that said, I would do more than just check the order of the plug wires you just put on, I would check each one to make sure you are actually getting spark through them. If you are, I would go with continuing to snoop around the cat being plugged. That sounds most logical at this point and with that many miles on your rig, very possible.