Got a 2017 330i and lately there's this metallic rattling sound coming from underneath when I rev the engine in park or neutral, especially around 2000 to 3000 RPM. It goes away when I'm driving which is weird. A buddy said it might be a loose heat shield but I crawled under there and everything seems tight. Another person mentioned it could be the exhaust flap or maybe the catalytic converter internals breaking apart. I'm trying to find a shop that can put it on a lift and actually track down the noise instead of just guessing. I've been looking for Advanced Exhaust Abu Dhabi Repair that has experience with the B48 exhaust systems because I don't wanna replace a whole section only to find out it was a bracket or a worn hanger. Has anyone dealt with a similar rattle on the G20 or F30 generation? Also wondering if a failing flex pipe could make that kind of noise. The car runs fine otherwise, no power loss or check engine light, but the noise is driving me nuts and I'm worried something might fall off eventually. Any tips on what to check first or good exhaust shops in Abu Dhabi that won't rip me off would be much appreciated. Thanks guys.