Sorry To say Tunnie Sounds Exactly the same as what mine was like
Heres is one to try make sure the Header tank is full run engine for abit then leave it over night if it misfires when starting and then clears after acouple of revs then its the head gasket.
Water leaks into one of the pots causing the misfire on startup after standing over night the engine quickly burns off the water.
get sniffing the header tank.
I had loss of coolent oil was fine dipstick was fine as the head Gasket had gone between the coolent and pot.
The HVB you cant miss it get under the Steering Box and its stright up and on the left hand side