2008 BMW 328i fuel regulator

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I have a 2008 BMW 328i convertible, with 88,000 miles on. Have been having trouble with car stalling out after installation of a fuel regulator, it stalls out within 10 miles after fill up. Then starts back up and no problems until next time fuel is put into the tank. I am getting misfire codes when this happens. The fuel pump was replace 3 years ago. I have had the fuel regulator out once since this happened. Any thoughts on what I should look into next?
thanks