Originally Posted by JBrady

PD, you are truly an expert on our 2nd Gen LS400s. That said I have a slightly different opinion when it comes to exhaust and headers on these cars. The problem with the S&S headers was not that they were cheaply made. The cracking problem was a function of the design (my choice) of a mini Tri-Y design. This caused a significant difference in expansion rates between the short and long tubes plus the additional hardening (more brittle) of the tubing at the additional weld points. I still believe that this design is better for torque but I agree that the PPE parts being 4-1 are less failure prone.

Regarding changes to the pipes I suggest keeping the front Y pipe and even the rear Y pipe and then replacing the middle mufflers with round straight through 2.0” resonators (like Magnaflows) and possibly the rear mufflers or muffler delete. The center resonator can be replaced by a 2.5” straight through or with the slightly larger than stock GS400 center resonator (55mm vs 60mm, 2.2” vs 2.36”, LS400 vs GS400). The front Y pipe works better than most can fabricate and the rear is decent. 2.0” is fine as long as mandrel bends are used otherwise 2.25.