k12 lumpy idle

Hi guys . Hoping you can help . 04 plate k12 was running great ,but has now developed a lumpy idle .
Also it turns and stats from cold ,runs lumpy for a few seconds then cuts out ..but only sometimes .
Cleaned throttle body ,cam sensor etc with a small improvement but it's still lumpy especially between 1 and 2 thousand revs . Seems to rum fine after that .appears to be slightly down on power too ..appears by ideas ?
Thanks in advance
Is there signs of oil on the plastic cover, or around it?
Have you changed the sparkplugs? Are they ok?
If you have oil on/arround the air filter box, then you need to change the 4 rubber gaskets underneath the sparkplugs.
The oil arround the sparkplugs conectors make them to discharge uncontrolled.
The fuel filter needs to be checked, as well.
Also, the sparkplug connectors might be broken.
There are several thing to check in this matter.. mainly ignition, and fuel system.

Hope it helps, as my english is not very good, my native language is Romanian