After having the entire turbo engine replaced (suspected based on my own investigation is a shaft bearing failure) we always have to have the air on recirculating otherwise as soon as we are behind another vehicle we get a ‘taste’ of their exhaust. The dealer replaced the hepa filter, but it did not help. Any ideas what this may be? Possibly something that was missed after the engine got replaced?
The connection from your exhaust to your turbo downpipe(exit) may not be properly fitted and leaking.