300tdi misfire

I hope somone can help here because im stummped!! weve had a 300 tdi discovery come in with a missfire, it does somtime struggle to start with loads of white smoke just as though the plugs are not working, but they are all fine. when it is running tickover seems ok but as soon as you go to rev it up it misfirers and chuffs white smoke out a little, when you drive it it black smokes alot. ive checked the timing, the bottom sprocket, the valve clearances, the lift pump the turbo all ok. the one thing i did notice is i am not getting hardly any deisel coming from the spill off pipes at any point through the rev range. can anyone shed some light on my little problem? oh and its an auto so running on EDC.

well found the problem, bent con rod on number 4 !!!!!!!!