Hello I'm in need of some advice and help. I have an 2006 A4 2.0TFSI and the brake pedal is rock hard when idling and driving slowly, but when driving and the engine revs where higher the brake pedal came back at times'but not all the time. I suspect a vacuum issue is the blame but what part of the vacuum system I'm not sure. I used a vacuum tester to check test the system and I'm getting none or very little vacuum. I've first thought it could of been the vacuum pump on the back of the engine that runs off the exhaust camshaft so replaced it making no difference at all. I replaced the PCV valve on to of the engine also. After not having any luck my next step was to make sure the servo was working by taking a vacuum feed from the intake manifold directly to the servo feed pipe and when I started the car the was a good brake pedal so I can rule out the servo being the problem. But now I running out of ideas as to where the vacuum is going and why the is such a lack of it. All the vacuum lines have been checked for leaks and some even replaced if the even looked slightly suspicious. Could the vacuum pump not be drawing enough air in due to a blockage somewhere in the engine itself or is the anything else I need to checked first.
Any help or advice would be greatly appreciated.
