The P5 is a Novarossi based engine, it is marketed under several brand names such as Noarossi,Tops,Rex,Crono, and a few others...not to mention modified versions such as JP,EB, RB,and Hot mods...all good engines that will work well with the 086 pipe
RB Concept engines are are all very good too, however pipe selection becomes an issue depending on what model you choose.