I jsut read

"If you have terminal 3 in your diagnositic connector then check your lambda value first. 50% is normal for most engines but the 103 engine (which I presume you have) prefers to run at 30-40% (I put it on 35% during services), they run quite well at this mixture, 50% is too lean on acceleration from experience. You can check you EHA (if fitted) for operation by watching the lambda value fluctuate +-5%."

so I guess my values of 33-35 are ok?