Disco 200 td G Reg

Hi All

I'm Not Shaw What's Wrong With My Old Disco
So I Have Some Other Questions

When Engine Starts It Miss Fires as Thou Its Very
Tight & Wont Rev Until Half Throttle Then Clouds
of Smoke All The Time From Exhaust Evan on Low
Revs HeadGasket or Piston or Fuel ?

Any Info

Regards

Jb