I did but only a very slight amount. The gasket size was real close as it was. Just did enough to blend them to the gaskets and headers. I took out any flashing and polished them then re-flowed them. Actually lost 3-4 cfm below .300 lift and only gained 10 cfm at .550 and 16 at .600 lift. IMO it wasn't worth the time and effort especially since my engine build is very mild. As CB said they flow really well when stock.
