92 Landrover disco splutter

Hello we have a 92 Disco V8i,it started running rough suddenly like if the engines wet all the filters/leads and spark plugs have been replaced but after a 2min run all the spark plugs had blackened and it's chuffing black smoke. I suspect it maybe the distributer cap or airflow meter?? Please if anyone has any ideas that would be awesome.

Cheers Deta