Does it feel like you've lost any power with the extra small oval muffler?

I am not sure. One thing about these 1.5 scroll headers is that they are smoother and the curves are fuller. This gives a feeling of it being slower except that the speedo moves quicker and you are carrying more speed.

I have sent of the logs so will tweak the tune slightly but it shouldn't make too much difference as it is still just a three inch straight through.