Ex Auto sparks fully conversant with Bosch "K & KE " you say spray a little Fuel in Air intake...fires right away...but are you able to drive off normal without lots of "spluttering / poping back / wont pick up properly till warmed up...this tell me something. You see the 5th injector should be doing "what your doing with spraying direct to manifold...So hear is what happens when you first go to start from cold, you turn on ignition, the water Temp sensor [ Yellow ] would adjust the Black ECU as to what voltage to be sent to the "Pressure actuator on the side of the metering unit"... this is so the pressure can be increased...now turning the Key to start fuel is spayed into manifold...so engine bursts into life...to keep it running now on all 4 injectors the pressure will Higher...how high depends on outside Temp as well as water Temp, also the engine idle will be higher 1000 / 1100 RPM this is set by the Idle control valve under manifold, as the engine warms up...idle returns to normal idle 850 900 RPM, so 2 items need Testing...is the 5th injector getting 12v on a Cold start [ only ].....next is the pressure actuator getting Voltage also on Cold start only...what i can say no voltage at pressure actuator, the engine would be a pig to start...firing...then petering out...keep doing this till eventualy runs. so hope of help. Pete .