I have been toying with the notion of porting a head for my omni, and just wanted some ARFCOM feedback on who is doind it themselves. There is a load of info on the subject, but not many people who pursue it due to the difficulty, and time involved. How about you?

I've never had the balls to try porting. It aint easy. There is a reason headwork costs big $. Very easy to do more harm than good. But I have never had a multitude of spare parts laying around to test my hand on either. If I did my answer might be different.

Never anything custom.  I've just cleaned up casting imperfections, polished exhaust ports, and matched the ports to the manifolds.

I do not do any heavy porting on my own. But I to clean up the bowls, match the ports, polish and unshroud the valves. Like said above, you start cutting too much you are liable to really cause some problems. That said, even the little porting I do is slow and painstakingly meticulous. It takes several hours to do one head.

My buddy has a flow bench at his house so when he ported his first set of heads he did a little experiment. First he flowed the stock heads and recorded the info.  Then he did his port work the way he had researched beforehand.  Next he put the head back on the flowbench to ck his numbers.  The flow had drastically decreased! It took him quite a bit of work to get them where there was actually any improvement. Luckily there was enough material there to work with or the heads would've been ruined.
Now imagine not having a flow bench or experience. You grind away for hours and think you've done some good but are clueless that you've done only harm.
Whenever I'm at a swap meet and see heads for sale that say they've been ported, I avoid them like the plague.  Most people don't have flow benchs at their houses and neither do alot of machine shops.
The only substitute for a flow bench is experience gained by having used one in the past on a particular casting.  Unless its just removing casting flash or port matching like you other guys have done.

EXACTLY!!! Without a flow bench you have no idea what you have done. Well until you install the heads and have less power than you did before. Now a bit of port matching and cleaning up is a different story.

Don't do it. On a car like that P&P won't do anything positive unless you address the entire induction system and valvetrain etc. In many cases porting alone may decrease stability at idle, and may cause power loss and a host of other driveability problems. In the end, porting alone is not going to do anything substantial when it comes to power. Build your motor first, get as much power out of it as you can. If you feel there is still a better flow to be had then port/polish your heads and intake for the last few HP, but please use an experienced shop, it's not really a DIY thing.