Yes mate it's definately worth changing the manifold, you will get better performance. Also you have probably read about it already, there is a restriction on runner #3 which is no good for the 3rd cylinder. The design of the manifold is important and also the material, it's no good getting a cheapy stainless steel one off ebay they will just crack but at the same time some manifolds can be quite expensive. I think the SPS ones are good value and I've seen loads of positive comments about them on here and TGTT.