[Goat Blower]

If you're talking about Shep, he switched to the same 3.5" Buschur system I have a fewy years ago. Then he went to a shorty pipe out the front bumper last year. I've only heard of three actual 4" systems on DSM's. Trust me, the 3.5" is plenty huge.

I've never seen actual back to back comparisons above 3" systems. But rough guesstimation by some NABR big hitters says a true 3" system isn't a restriction until at least 550 whp.