HI,

Could be so many things, but check the cold start function ie, the
cold start valve is working , if not check that power is going to it from
cold, if no power check the thermo time switch in the inlet manifold
(underneath , it is brown ) also the wiring to the cold start valve has no breaks, the thermo switch controls the power to the cold start valve
but for only a short time, the fuel ecu controls warm up enrichment,
starting enrichment, acceleration & full load enrichment etc, through the fuel pressure actuator,
also check you have no air leaks on any of the hoses to and from the turbo to engine inlet, ( if large air leak it wont idle RS turbo escort)
and check the auxillary air device is working,(open & closing)open when
cold,

DAVE R.