Defo fuelling issue not plug issue, the plug/s are being killed by most likely a crap injector, as you've been told, try swapping the injectors round and see if the plug problem moves with the injectors, or have them cleaned, even diy in a ultrasonic cleaner £20 from lidl.
Worth trying some fuel system cleaners such as wynns, but don't think it will cure it.
Once it is running nice and hot I would check the co.
tabetha