Okay, here is the story. A customer brought in today a 2001 xj8 with the 4.0 engine. Has been run in RP mode for a while. While driving today car was run out of gas. There is now gas in the car and it runs but making popping noise coming from top of intake (or at least that is where it seems to be coming from). It sounds as if it is a engine being run with no exhaust at all.

codes present - p0300 - 0304, p0112, p1000.

Have looked at the spark plugs and all seemed to be pretty crappy but I have not checked the gap yet. Fuel pressure is fine.

Apparently one of the timing tensioners was recently replaced and ever since then car has been in RP mode with multiple misfires.

My questions are:

What would cause that popping? Could it be the misfires? Intake Manifold or catalytic converter problem?
On Alldata, it shows bank one being the left if you are standing in front of the car. It also shows the firing order as 1-4 (front to back) for both sides. So how do you tell which bank the misfire is coming from if they are both going 1-4 as opposed to the 1-4 then 5-8.

Any help would be greatly appreciated, I am a general mechanic not a Jaguar specialist, but I would like to try and help the guy out as well as learn something new.