740GLE wont run properly over 2000revs

Also could be worth checking the main engine earth strap(s) pictured below, Make sure its not freyed and that at each end the strap and anchor point is clean(good contact) and tightly bolted down

thanks 

thank you both for advice, have been driving it gingerly today but seems to be getting worse, rev needle will drop like a stone and loss of power every now and then... at any revs now, then will come back. Have day off tomorrow so am going to check the things you have said. Paul J

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