I recently had my power steering pump replaced, and since then it hasn't been the same. When steering, there is a low groaning noise, moreso if it's raining or humid outside. The fluid level seems fine; however I am concerned they used the wrong fluid. What is the appropriate P/S fluid for a 2004 Audi A4 Quattro 3.0 with 114k miles? The fluid in there looks yellowish. What else could be causing this groaning?