Volkswagen Tiguan - Stalling , No Start Condition

Vehicle towed in with an intermittent stalling and eventually a no start condition. The vehicle would crank but no start. Upon pre scan report, the following fault codes were stored within the Engine control module:
P0351, P0352, P0300, P0301, P0302, P03045
I realized the vehicle would start when I would apply throttle. Once the vehicle started, the engine would stay running as long as the RPM's did not drop to idle. Otherwise the engine would stall again and was difficult to start back. Initial diagnosis revealed a faulty crankcase ventilation housing which resulted in a large "internal vacuum leak". Once the crankcase vent was replaced, the vehicle would start and run perfectly until the road test. The road test found an additional fault that would have not been recognized otherwise. During the road test, the engine would intermittently stall out but I could coast to a parking lot, stop and would typically start back. During this entire road test with stalling happening, zero engine fault codes were stored. Once back at the shop and on the lift, we observed the engine speed sensor. Upon visual inspection of the speed sensor, we found an additional problem. The engine speed sensor connector housing was full of engine oil and the locking tab for the speed sensor connector was broken off allowing the wiring harness to become loose from the sensor.
We replaced the fault sensor and connector so the connection would be secure. The next test drive was 100% successful. No more stalling or intermittent no starts.
This is a prime example of why it is very important for us technicians to perform a quality post repair road test. This is also a prime example of why we as technicians can not accept "fault codes" as the only basis for our diagnosis. This vehicle could have been so easily misdiagnosed. Proper diagnosis must also be thorough diagnosis.