GT86 Engine Stalling After Fuel Filter Change

Sounds plausible. A pressure drop after a fuel filter change often points to regulator issues. Have you checked the fuel rail pressure? A simple scan tool should give you a reading. Also, listen closely to the fuel pump; is it unusually noisy?

I don't have a way to check the fuel rail pressure myself. I listened to the fuel pump, and it sounds normal. Could a faulty fuel pump relay cause the same problems, or is the pressure regulator the more likely culprit since it started after the filter change?

While a faulty relay is possible, the timing with your fuel filter change strongly suggests the regulator. The error entry likely confirms this. A proper diagnosis requires checking the fuel pressure; I'd recommend a workshop visit. It's probably just a bad regulator, but better safe than sorry when it comes to the fuel system.

Took your advice and brought it to a local workshop. You were right, the fuel pressure regulator was bad. Repair cost 45€. All fixed now. Thanks again!