weird running fault on 200tdi

hello...ive got a 200tdi powered series... its been puffing out blue /grey smoke excessively and when revved sounds like its misfiring as such ....checked all pipes ..changed fuel filter.. removed injectors and they all seem to atomise as far as you can tell without proper testing... checked timing and its spot on other than the cambelt has worn almost half way through by wearing on the cover !! ( presumably a separate fault but any ideas appreciated) so I removed the head and no1 and 4 have clearly been over fueling as the carbons all soft and shiny black plus it can be seen down the exhaust header oily and wet just on 1 and 4 ..head gasket looked quite new and no signs of leaks... any ideas???