Hello everybody, I hope you can help me!

We recently had a blowing injector replaced (it blew on the motorway, puff of white smoke engine management light on, chuffing noise) Now we have a problem which I suspect is another injector, where from cold, the car runs on 3 cylinders until hitting (mostimes) 3 on the temperature bar. If I turn the engine off and restart, it runs on 4, the management light stays on but comes out of limp mode, eventually going off of it's own accord. The car will then run happily all day, no warning lights, goes up and down hills without loss of power and so on, until left for a few hours, then it starts again.

The car has been serviced in accordence with Citroens recommendations and had a new fuel pump fitted. Any ideas before spending another wedge on an injector replacement?