UK Car Repair: jaguar xj6 starts and runs great ,until i press accelerator, throttle position sensor, egr valve

Question
i have a jaguar xj6 6 cyl. the car is one of my prized possessions , ok i have done all of the regualr tune up things changed plugs and wires distributor caps rotor button i even changed pump and filter along with cleaning gas tank , changed oil and tans fluid . i can get into the car and turn the key and it will start up just as smooth , run for a few minutes and die . if i press the gas pedal to give it more gas it will run but it idles ruff and sputters like crazy and backfire from the breather this is while depresing the gas there are times i can just start it without with the key and it will run i get a pro code of fuel failure 37 whihc i cant seem to find anyone who knows what this code stands for or means i am certain its something simple i just want to drive my car please any advice you can give which may help me get pointed in the right direction  

Answer
Ok, Code 37 lists a 02 fault due to two things. A: the oxygen level is high and the hydrocarbon level is low. B: the signal from the Throttle position sensor does not match the signal from the air meter. If you have an older XJ6 it will have a vane air meter that may be faulty. You could also have a bad EGR valve and possibly a blockage in the system. Most plug up in the manifold port or the tube going to the EGR valve. I suggest you check the wiring and vacuum lines for the EGR and also the EGR temp sensor. If you find no problems I suggest then removing the EGR components and cleaning them with carb cleaner and a stiff copper wire to poke at the solidified carbon build up. Once you have done this you can focus on the intake port and do the same thing except change to a cleaning solvent called throttle body and intake cleaner. Once you have gotten a fair amount of the crap out of it you can then reassemble and test it. If that has no impact, you can replace the air meter and throttle position sensor. However; this still may not solve the problem. I will put it to you to get it into a garage with a Diagnostic Scan Tool. I am assuming this car is pre 1995 production and it will be fairly easy to diagnose with a comprehensive diagnostic tool. If you do not agree with that, following the steps I explained will go through the possibilities in the order of least expensive to most.

Regards,

John