Speed sensor G28, ignition failure Speed >3,500Umin

Hello dear V8 friends,
before I explain my problem, I would like to introduce myself and my V8.
My name is Reiner and I've been retired since this year. Since 1993 I am proud second owner of a wine red Audi V8 3.6l automatic Bj. 1991 with now 350K km mileage. As a special feature, I would like to mention that the thickness was never moved in winter, was always in a garage and was logged out from 2001 to 2011.
Now my current IST problem:
==References====External links== 3500 rpm of ignition oscillators and the fault diagnosis with my own Diag device V.A.G. 1551 returns error code 00513 encoder for engine speed G28 "Unplausible signal, No signal".
Up to this speed range, the thickness runs perfectly without any sounding.
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Chronicle what happened and what was done:
On 03.08.2016 right after the start I already noticed that the engine somehow did not run round and also did not really want to take gas. After about 1km the alarm light CAT lit up and I sneaked with the car to a station bay from where it was then towed via the AvD to the next workshop.
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What has been done so far in the last week:
The fault diagnosis resulted in code 00513 and 00514 both G28 speed encoders for engine speed and G4 for ignition time (OT).
Both encoders were renewed and the case of the old G4 encoder showed mechanical action. (several small dents)
After the installation of the new encoder, driving behaviour has improved only slightly. It was only possible to give up to approx. 100km/h. In normal acceleration, false ignitions started immediately.
Now the control unit was replaced and also checked on the flywheel of the gear wreath with cylinder pin for OT Geber. No damage was detected on the tooth wreath and cylinder pin. Now I and my workshop (Bosch) don't know any more. See above IST – Problem.
What else could be the cause of the error and can someone in the Landau Pfalz area recommend me a competent company, expert?

Best regards
Pure