This may be over simplified, but I think I would be lookin' for an older set of them "N" heads. Seems to me that the "new" N head has probably been redesigned and therefore, "screwed-up". Sounds like the newer heads don't produce the usable torque that the old ones were capable of. Also I think that ANY cylinder head that wont let you put more than 31* of timing in there, is a piece of crap anyhow.
JMO and only that.