My 596's aren't stock. I spent a few days grinding in the pockets and also paid to have the machine shop cleaned up as well, but like you said I don't think it has an all-out effort inside the heads that I have. I could definitely do some intake Port matching that would probably help.
Lets just say this... ive spent a week+ at a time developing a port flow profile. Its time consuming, thats why its costly sometimes and or dying off..
I port per motor requirement.