if i get a street port and polish on my ED XR6 head how much power will it give me?

anywhere between 5 to 30 kw if using a flow bench. that also depends on the other mods you've done & the amount of bucks you're willing to spend on it.

first of all, you gotta let the mechanist know what power you expect from your current configuration right throu the rev range. every thing has to match up.