Good point!
I know Honda's golden boy the NSX Type R was a 3.2 V-6 making 290 hp & the NSX in general was considered the best NA performer for most of it's loooooong 15 year run.
So, I really can't think of a production V-6 with higher numbers besides the Nismo Fairlady 380RS mentioned already ; )
Fairlady Z Version NISMO Type 380RS DEBUT!!