One problem related to manifold/header/muffler/tail pipe has been reported for the 2003 Nissan 350Z. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2003 Nissan 350Z based on all problems reported for the 2003 350Z.
2003 Nissan 350z brought in to showcase Nissan in bourne, MA with oil light on and no oil pressure. Technician put car on lift and drained "less than a pint of oil" from vehical. Inside of tail pipes were oily and black. Milage at the time was 14,100. Nissan's solution was to do consumption tests at 500 mile intervals which resulted in oil usage of 1/4 to 1/2 quart per 500 miles which Nissan claims is "normal".