Thanks for the advice guys, wont bother with the manifolds then. Will still try to push for 300 with the exhaust system, remap and Kinetix manifold (already in the post ).
As far as weight saving goes I was always going to change the seats anyway, fancy some bride recliners. I will look at other places I can shed weight, I've already got rid of the spare wheel and jack, as well as some lightened suspension components.
Where are the other places I can easily lose weight?