Today, the constant reduction of development time, the need to reduce cost & weight and increase of complexity create the need of constant improvement of the CAE methods used to develop automotive parts such as exhaust system components. The use of dynamic transient simulation and subsequent damage calculation for road excitation is state of the art in the automotive industry. The problem of this method is the long calculation time & big data produced as well as the precise knowledge of the test track (profile) needed. Those tracks are generally not communicated by the OEM to suppliers. Frequency domain methods for fatigue analysis and/or for general random response analysis have experienced resurgence over the last few years due to improved technology and better computational processes. The proposed paper will propose a possible alternative to the use of the transient method for the development of exhaust system using the capabilities frequency based fatigue method in a realistic case under multi-position/ multi-directional excitation. The key steps of such a frequency domain analysis will then be discussed in the presentation. The first relates to the conversion of the multi-channel load time histories. The second relates to how boundary conditions are placed. Both these topics will be covered in detail. Then, the frequency domain results will be compared in detail with traditional time based results. As conclusion & outlook, the possible opportunities of those spectral methods to improve the cooperation OEM/supplier without compromising any precise information about tracks profile using PSD will be displayed.