Juergen,

When your model is on the table, is it horizontal, or tilted nose up, like on the runway?
It must be in the runway position.

The fuel line from the tank, to the high-speed needle, to the carburettor; are they as straight and as short as possible, or with kinks and loops (to facilitate refueling)... Make sure they are straight and short.

Break-in; how did you do it (although it should also affect "table manners")?

I cannot think of anything else. Can you take a web cam picture of your engine and piping and add it to the message?

If all else fails, you could ask OS through the forum (down below).

Sincerely,