Mmm I'm not sure on that servo as I have never used one, maybe your horn could be slipping on the splines on the servo? Have you by mistake put the wrong horn on? A 25 spline horn on a 24 spline servo for example would kind of work but it would slip round. Just an idea?
Ansmann parts are abit tricky as they stopped bringing them into the uk but then another company took over so I assume they are still available but where I'm not sure?
Try SMD (spire model distribution) they bring Team C cars into the uk, I'm not sure of the politics of it all but Ansmann cars are rebadged Team C cars.so most parts should be compatible.
Here are the kyosho gears that I believe will fit
http://www.jemodels.com/electric-mod...tegory_id=1285
Generally what the manual tells you won't be a million miles away on the slipper clutch but obviously the is tolerance in the parts, track conditions differ and what motors are being used cannot all be covered, I should be there on Sunday, I run a kyosho lazer that is a similar car to what you have so I can tak a look for you, but most reasonably experienced racers should be able to help also