Maybe I've learned a good lesson . . .

That gets back to how effective are dynos in replicating the low rpm loads?
If the chassis dyno is anything close to repeatable, then below intestate speeds, the van was less torquey and less responsive at full throttle with the ported heads, cam, and 4 bbl than it had been as a 2 bbl. The saving grace is part throttle kickdown of the transmission.
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wonder when back in the van if he put stock manifold exhaust back on plus breather, might also took some out of the tune.