Take a look at the intake i did.
http://www.imagestation.com/mypictur...mp;caption=EFI SPYDER&album_id=4287153843&from_album=1
I didn't smooth out the lower part but if you notice i did smooth out the elbow. I used a die grinder and the sandpaper rolls that are for porting and polishing. I sanded it till the casting marks went away. The only thing is i think it made it out gas worse than if i would have left it alone. the lower part of the intake did not out gas. I stripped the elbow down 3 times and ended up using Metal-2-Metal to skim over where it was out gasing. That fixed all my problems then. Caswell sells Lab Metal and it says you can thin it out to spray it.
http://www.caswellplating.com/aids/labmetal.html
Then you could sand it smooth to eliminate the out gassing too. Never tried that stuff yet.