Ok, this is what I haven received back from a knowledgable Rover person. (read the leak down fuel pressure part, I forgot about that... pressure at the rail at start up is good, but how long does pressure stay there?
First things first.... This cat needs a Service Manual. He is playing part darts hoping to stumple on the right part..... Testing is the order of the day.
A Gasoline engine, from Acura to Volvo needs 5 thing to fire..
1) Air
2) Fuel
3) Compression
4) Spark
5) Timing.
If you have a misfire, one (maybe more) of the 5 is missing. First thing is to figure what is missing..
He needs to confirm Fuel Pressure, and that it isnt bleeding down.
Whos spark plugs did he use?
Timing is tough to test on a GEMS car, but if the other cylinders are firing ok, it's likely good.
He tested compression... His was a little high, but I wouldnt worry. A vacuum gauge would help him check for sticking valves..(VERY possible in a 96)
And, he needs a service manual.