This for example

On the face of it it looks quite smart, but the guides have not been cut back, and although the finish on the ports is alright i think material had just been removed, this is not the aim of the game, you want to decrease restriction to flow WITHOUT damaging the heads ability to create mixture swirl or loose gas velocity, By just straightening a CVH inlet port you create quite a large void behind the valve, if you go from a small diameter tube to a large one (which essentially you would do) the gas velocity decreases and the mixture 'stalls' behind the valve not good, if any thing you want the mixture to increase in speed behind the valve.

This is basically what i have read and learnt from talking to pretty knowledgeable people, but i haven't done it and would really appreciate some advice from the guys who have.

Rob,