Hi, thanks for your answer.Vacuum leak from booster is my guess. Especially if only happens when brakes are applied.
Good luck finding the issue and Happy Holidays
Brake Booster has been checked and has no leaks. When you press brake pedal in neutral or in parking , there is no drop in idle speed.
When you press brake pedal in drive but you manually press the brake pedal switch ( wich is located below the dashboard ), there is no drop in idle speed either, so I relate the problem with the signal sent by the switch to the ECUs.