Hey there, I had similar issues with my 2016 Porsche Boxster last year. The symptoms you're describing sound exactly like what I experienced, rough running, black smoke, and stalling. Initially thought it was the fuel sensor too, but when I finally took it to the dealer, it turned out to be corroded cable connections to the fuel pump and multiple sensors. The main problem was moisture getting into the connections over time, causing faulty readings and irregular fuel delivery. The fix involved replacing several wiring harnesses and cleaning/resealing all the connections. It was a serious job that took about two days to complete, but it solved all those issues completely. My Boxster's been running smoothly since then (now at 156k km). If you're experiencing these symptoms, I wouldn't wait too long to get it checked, faulty connections can cause more damage if left unaddressed. I know you're hesitant about mechanics, but with these symptoms, I'd recommend going straight to a certified Porsche specialist. Good luck!

Thanks for sharing your experience! That's really helpful to know about the wiring harnesses and connections, sounds exactly like what I'm dealing with. Do you remember roughly how much the repair set you back? Also, has everything stayed good since the fix, or have you noticed any other quirks pop up?

Hey again! Happy to give you an update! After getting my Boxster fixed, I'm glad to report that everything's been running like a dream. The mechanic actually found that the Low pressure fuel system sensor wasn't working because of those dodgy cable connections I mentioned before. They sorted it all out for €95, which was honestly a relief, I was expecting way worse! Since the repair, my car's been perfect, no more black smoke, no stalling, and the power's back to normal. It's been about 8 months now, and I haven't had a single issue pop up. Best money I've spent on the car, honestly! The mechanic did a top job cleaning and resealing everything properly, so no more moisture getting where it shouldn't. I know you were worried about finding a good mechanic, but honestly, sometimes these electrical gremlins are pretty straightforward once you get them sorted by the right expert. My Boxster's now at 162k km and purring like a kitten! Let me know how you get on with yours!

Thanks so much for all the details! Just wanted to update you, I finally took your advice and got my Cayman checked out yesterday. You were spot on about those connections! Took it to a certified Porsche specialist in town, and they found pretty much the same issue, corroded wiring and sensor connections. The whole job cost me €110, which was such a relief after imagining the worst. They had my car for about 6 hours, cleaned everything up, replaced some damaged wiring, and properly sealed all the connections. The difference is like night and day, no more black smoke, stalling's gone, and she's got her power back! Funny how we worry about these things being major problems when sometimes it's just a matter of finding the right mechanic. Really appreciate your help pointing me in the right direction. The car's running beautifully now, and I've even saved that mechanic's number for future reference. Thanks again for sharing your experience, it really helped me make the right call!