[wslade2]

I’m normally aspirated so little experience with 337 turbo. But have good deal experience with ground based turbo diesels.

Looks like good list.

Exhaust leaks are under appreciated and can be hard to find with surprising effect on turbo performance. The exhaust system lives in a tough environment so very much at risk. Exhaust leaking at the cylinder of course are their own doubly problematic issue. Also, if you have intercooler don’t forget to look at that. They can shake and crack with a resultant leak.

Air filters get overlooked because they look fine but at a micro level can get obstructed.

Frequently there’s a perfect storm of a little bit of everything: declining turbo, induction leaking, exhaust leaking, dirty filter. Don’t just jump in and sentence your turbo as guilty until you look at everything.

Of course carefully check for turbo shaft play and any rubbing on the housing or oil leaking out of the turbo into induction or exhaust. Any increased oil consumption?