Basic Porting 101
As with 95% of the production heads out there, the best gains are to be had with a good bowl blending, and if possible to raise the roof of the exhaust port as much as you can, which with water jackets and other stuff to get in the way, if you can go up 1/4 inch, thats a lot.
The idea is to take some of the angle out of the turn at the bowl, but undercutting the floor side of the bowl and to slightly decrease the angle between the bend in the runner and the exhaust port. You will want to take out a little more from the port side than at the bend, and keep the roof in as straight of a line as possible to that bend.
Some gain can be had by slightly widening the port as well. As a general rule, doing any grinding on the floor will only take you backwards.
If you have some good pictures of ports to look at, you can see these are the basic manouvers.
This is a very basic instruction on porting, and not to be construed as total gospel in all occasions.
Just remember; A little bit is good,but a bunch aint always gooder.
The basic idea is to try to equalize the flow in the runner, so that you have as much flow at the port as you do the valve throat. Meaning that you want them to have as close to the same cross section as possible, and to keep that uniform all the way from one end to the other.