Fuel boost pump is not working in "low" position. It's an M20K, S/N 25-1187. We're doing an annual inspection and need to fix the issue. After troubleshooting, it appears the boost pump regulator P/N 880047-503 (model VR536) is bad. We can't find a new one. Anybody know of a shop that can repair this one? Or where we can buy a new or serviceable one? It's an Electrodelta part. Thanks!