1998 Chevy Venture 1998 Chevy Venture loses oil pressure on

The Oil pressure light on my 1998 chevy venture comes on whenever I make a sharp left hand turn. The car currently has 135,000 miles and at 102,000 miles the engine was replaced. I have owned the car since the engine was replaced. I noticed the light back at 102,000 miles and thought that it was caused by a faulty oil pressure switch. I had the oil pressure switch changed twice and it has not resolved the problem. I have put 35,000 on the car, most of them have been highway so I rarely saw the light. I have had no other symptoms or problems. When the light illuminates the longest it has ever lasted was about 4 seconds.