I've heard of some pretty amazing things being done with the e6 heads. I don't have any flow data on ported versions though. Most of the gains were the result of reshaping the cumbustion chambers and unshrouding the valves.
Your local machine shop would be a good source. You could also do a search for "e6 heads" in your internet search engine. I've come across various articles from time to time. I'll be looking into a little more myself here in the very near future as I plan to remove my heads and swap the stockers back in to prep these for a new combo. The headwork is not something that I could attempt on my own.
none of my local machine shops are doing any "custom" headwork other than 3-angle valve jobs, until thier work slows down
if i were to try unshrouding the intake valves myself.......and if i didn't do it properly would it make my car run worse than stock?........or would it have to be done professionally for the car to run right?
im rebuilding the motor right now......and a friend offered me a $150 and a set of "freshly worked" D80Es for the e7s i was previously running.
So im most likely going back to the e6s and i would like for the car to run pretty good.