Throwin' Codes p0300 and p0302
 

I was doing about 80 mph down the highway and I heard some unusual whirring sounds. I looked down just in time to see the oil light come on, isn't that a great feeling?! Anyway I pulled over and it was obvious I had some valves ticking hard, I checked the oil and everything looked great. I never felt the truck misfire but the codes were telling me otherwise. I was able to let the truck sit for about 14 hours and when I started it again no oil light and no valve noise. I am planning to change out the wires and clean the mass air but if the valves are not ticking should I get in there with the feeler gauge anyway? I am capable of doing the work but I have never performed it on a Disco. Also the CEL NEVER came on. I noticed when I changed the plugs about 5 months ago that my wires have the cylinder designation on them, could this mean that they are the original wires?

I would figure out the oil psi issue before doing anything else.
What type and weight of oil are you using and are what grade of gas are you running?

Pensoil 10w-40, mid grade gas.

Get off the mid-grade gas, DO NOT clean the MAF unless you have an extra $260 for a new one, and as Spike said, oil issue first.
How often do you change your oil, what brand of filter do you run? I would suggest you pull the oil pan and see how dirty it is and if your pick up tube is plugged, clean everything reinstall then have some one perform an oil pressure test, cold at idle, 2000 rpm's when cold, idle at operating temp and 2000 rpm's at operating temp. Do this exactly and get back to us with the numbers
As for the wires, it is time to order some 8 mm Magnecor wires.

The filter is Fram I believe and I change the oil every 3k on the nose. Is there anything I need to know about pulling the pan? I have performed this on Chevys and Jaguars but not on the Rover. And the MAF is a no-go? Ok?

MAF is a no go. Get rid of the Fram filter, they will cause dry starts with our engine.
The oil pan is an easy job, resealing with a paper filter and or sealant.

Alright, thanks guys. I will get started and post the results.