Land Rover Repair: Land Rover codes, mass air flow sensor, mass air flow

Question
I have a 2001 Land Rover Range Rover SE. It has 96,000 miles on it and is displaying 2 codes. The codes are 0304 and 0734. I know what each code is. The 0304 is a cylinder 4 misfire. I changed a couple spark plugs hoping this would clear the code. However it returned. The other code is a Gear 4 Incorrect Ratio. I checked online and was told to clean the Mass Air Flow sensor. I noticed it did need to be cleaned and did so. However this code still came back on.

Please give me your opinion as to what the problem is with each code. If you need any more information please feel free to email me at . Thanks

Answer
If you have a misfire that returned after changing a pl;ug the next stop is to change the wires and coil packs - a considerably bigger job.

With respect to the other code - we do no "clean" mass air sensors.  We replace them.  That's what I would do.