to answer your question 98blackcivic they flow virtually the same. they both have 28mm exhaust valves and 33mm intake valves. so the difference in flow is going to be in the B16 mani VS the GSR mani and also port matching. to got the most power out of the B16 Honda cast it as close as the could so that it would flow good. they did not focus on this with the GSR being that its a larger displacement engine and did not require such

If you port match a GSR Head and run a skunk2 mani on a B20 block. VS a B16 port matched with a skunk2 mani on a B20 block I willing to bet the GSR head would give more power.