I've got an intermittent problem that's come up on my 155 (1.8 16v). I've seen a couple of other threads posted which seem to describe similar symptoms, but there seem to have been several suggestions posted, so I thought I would describe mine in the hope that someone might be able to throw some light on it.
Occasionally the engine will hesitate when driving along - it's usually at constant throttle (e.g. on a motorway). I've noticed that it sometimes is accompanied by the injector light flashing on and off - but not always. Most of the time the car runs fine and ticks over very evenly. However, this evening for example I drove to Esher from Guildford (about 15 miles) up the A3 and it was really quite bad - lots of hesitation and jerking, with the injector light on and off (but not always at the same time as the hesitation). I left the car for around 20 mins in Esher to pick a couple of things up, and then drove back home the same route with no hint of any problems at all - the car didn't miss a beat.
Sometimes the engine revs will 'wobble' a bit on tickover, but generally it's really even.
One last thing - and this is probably a coincidence, but the n/s dipped beam has packed up this evening - I'll look at it tomorrow as it's probably just the bulb, but I though I would mention it in case thinks there might be a connection wrt relays, fuses, wiring.