1998 Nissan Sentra Water in engine oil

My Nissan Sentra GA14 engine (1998 model - fuel injection) was repaired for the second time because of water in engine oil. (The first was not successful). The head gasket was replaced, new water pump was replaced, sealed well the timing chain cover, oil and filter were changed. The engine was tested for more than 2 hours including the road test. Checked the oil and water after the engine cooled down and everything is fine. Oil was not contaminated. A Road test was done again for 20 minutes. The following morning before starting the engine I checked again the oil and it was ok. But after using the car for a 10 minute trip, the oil becomes milky again. The engine is not overheating and it's running very smoothly. There's again water in engine oil. Is it possible that it is caused by a defective intake manifold gasket. There's also water coming out of the tail pipe. Please help.