PowerPulse D5: “Emission scent” in the interior, hissing at the front left

In the meantime, it had several times the problem that it smelled like (diesel) exhaust in closed windows in the interior. On faster sections it does not occur, but often: – after engine start – on slow sections – on gradients. Have already experienced this in different places, so construction machine exhaust can exclude etc.. Independently of me this was also criticized on the passenger side… Maybe there is a connection here to my different exhaust pipes: left inside normal black, right inside virginally new. Does anyone have an idea? Thank you in advance.