My 4.1 didnt come with the arrestor installed. There is a ring in the end of the pipe, but its not holding anything in place. The hp gains that FMF claims for the 4.1 are without the arrestor.I just got my FMF 4.1 also, but have not installed them yet. When you guys talk about the loudness and the hp gain, is that with or without the spark arrestor?
I thought I had seen somewhere the claimed hp gains....anyone know if they were they with or without the arrestor?
The 2bros pipe Scuzz has is loud, with or without the arrestor, but its a nice deep loud.