Yep. Had this problem and it was head scratch time. I assume 6 weeks later you have either sorted it, or given up, either way here was my solution.
Stage one, I cleaned out the breather pipe from top of the engine oil filler to air intake near the air box. this was full of mayonnaise caused by a lot of short distance driving so engine was not hot enough to burn off steam in the engine. Then removed air pipe and air flow meter and removed sensors and intake manifold. Lots of gungy oily deposits were cleaned off everywhere and when all put back together ran a bit better, but not perfect.
Not all together satisfied i then bought some used (matching but different coded ) injectors off a Stilo 1.6, this cured the problem but was a fiddly job.
A few weeks later a loss of power was also found at low running speeds, as I heard a leak in the exhaust, this was traced to the manifold which was cracked. Having not found an economical new replacement I had this welded and since refitting I have had excellent running with no further issues.
As a belt and braces approach I also fitted a new coil pack and spark plugs and leads. All in all this little lot cost me about £200 and did my own work, very satisfying I might add. now looking forward to stripping the rear brakes and fitting a new CAT which annoyingly split on me last week :bang:
