I can tell much more just feeling a few things with my fingers. I've seen
many bad port jobs, and many more bad valve jobs. A bad valve job will ruin a head, and the things most inexperienced
people do with porting make no difference. You need a flow bench, valve grinding equipment and years of experience to port heads and get a real ET gain from them. It's 25 years of porting heads now for me, and I'm still learning.