1. Check Exhaust Gas Leak

WARNING: This page is about a different car, the 2004 Infiniti M45. However, it is still accessible from the selected car via links, so may be relevant.

Start engine and run it at idle.
Listen for an exhaust gas leak before three way catalyst (manifold).

Fig 1: Checking For Exhaust Leaks

Courtesy of NISSAN MOTOR CO., U.S.A.

OK or NG

OK: GO TO 2.
NG: Repair or replace.