Not exactly opened up, you can also use epoxies to make the ports smaller. This is generally why flow testing is done on a bench. If the ports are believed to be larger than necesary and not creating enough velocity then the epoxy can be applied to make the engine flow faster.Originally posted by jonesie
[br]it means that the exhaust ports have been opened up and smoothed out for more and better air flow. basically take a dremel or small grinder and open up the cylinder ports and passages to allow more air to flow. but if you have not done this before take it to someone as not doing it properly is going to make tuning hard as on cylinder may draw more air than another and cause tunning headache.