There is definitely a big difference between ported and non. Its not so much that you actually gain power out of increased airflow, but it doesn't build up as much carbon in the exhaust side and create hot spots, so more heat exits the cylinder combustion chamber which allows you to add more timing.

I don't have a print out, but on the dyno down at school I put down 208whp after just my street tuning. I'm guessing getting the heads broke in and the tune made a big difference. I don't think atmospheric changes at the same altitude would make up for 17 hp alone.