Re: My heads- what should i do
One other thing that you might want to check before you change to the GT40P's is that your current extractors will still fit. The bolt pattern will be the same, but the plugs are at a different angle, and MIGHT foul with the pipes. I must admit that i do not have the GT40P's, so cannot offer advice on what extractors will fit or not, but someone else might. Hopefully it won't be an issue, but you'd be pretty pissed if you get them and find you then have to get new extractors.
Either way, you might as well get the 1.7RR's and fit these at the same time. The yella terra ones will fit both heads.