The LS4 has a tiny cam and restrictive manfiolds. The heads are 243's, same as on the LS2 so I'm sure they flow pretty well but they're obviously not the choking point.

I just like to rib people when they say things like the L67 has no top end (in regard to power curve, gearing is a whoooooole nother' topic)

I could really send things into a frenzy by saying an L67 that makes the same peak whp as a stock LS1 has more top end than the stock LS1