Well it could not be seated properly up into the fuel rail where it's clipped in or when you put it in, an o-ring could have been pinched. I'd order the upper intake gasket and take that fuel rail off and double check it. I'm sure you can order some new oring kits off of ebay or you might have a spare still laying around. It's worth a shot.

 

I wanted to follow up to close out my own post.

I tore everything down to the rocker assemblies. I soaked the rocker assemblies and rocker covers in a strong degreaser (PurplePower) to clean them up. They were filthy. I also replaced the oil separator while I was at it. Nothing else was replaced besides the necessary gaskets/orings. After putting it all back together my misfires are gone. It could have been a very dirty/stuck rocker assembly component or an electrical connection that was reset more securely upon reassembly. Who knows. I'm just glad to have my Rover back!

Here is a pic of my initial reassembly with half-assed cleaning of the rocker assemblies:

Here is a pic after tearing back into it and giving the rocker assemblies a proper cleaning: