2002 MG ZR engine struggling in low revs

Basically my car has been off the road and not been used for the past 6 months, ive recently tried getting it going again and there is a delay when first starting the car before it actually turns over. Once running it revs ok but when under load and driving in low rpm it feels like the car is struggling and there is an occasional clunking noise coming from the under the bonnet and also the engine management light is coming too. Once it is up to around 4000 rpm it seems to sort its self out and drives ok. I have cleaned the air filter, checked the spark plugs gaps, checked the fuel pump is supplying enough fuel to the fuel injector.

Not sure what else to try, I tend do most work on my car myself so any further ideas which i could probably manage myself would be appreciated before i take it to a garage and to get robbed!

Thanks