Volvo 850 Stalls HELP

Before purchasing my 1994 Volvo 850 Wagon, the owner had his mechanic put in a new fuel pump and fuel filter. He said the fuel pump relay was relatively new. He did not put on the one I had sent.

The car stalls out, especially when going around a sharp corner like a freeway entrance ramp. Other times it does it randomly and will start after a minute or two and run perfectly until the next time.

Any ideas what else it could be. I do have the new fuel pump relay to install if that might be the problem. The car has been very well maintained. 160K miles. New timing belt 20K ago.

Thanks in advance for your kind replies.