Audi Repair: AUDI A4 Leak Detection Pump, wheel wells, audi a4

Question
I recently had my Audi A4 in the shop because there is smoke and a burning smell that is coming from the engine under the wheel wells. The service technician states that it is the Leak Detection Pump and the estimated cost of service is almost $500. Does this seem accurate? What is the leak detection pump?

Thank you for your time.  

Answer
hello
LDP pump making smoke??? LDP pump is locate it by left rear wheel, and I've never seen it making any smoke.
Pump itself is used by EVAP system to pressurize fuel tank and check for any vapor leak.Once something on the fuel system leaks - pump can't make a pressure and check engine comes ON with Evap fault. i think this system is only used on US models.
if your car is smoking and burning from the front and its smell like oil, most like it valve cover is leaking and oil drops down on exhaust.
good luck                    pltech