Cam Experts: Lobe Separation Angle?

Now the tinkerer in my wants to swap my 340 cam out for something with a narrower LSA just to see. I haven't even got the car on the road yet.
One thing that interests me is the variables that Erson mentions and how they affect performance with varying LSA. For example what happens when you have exhaust manifolds vs headers?
more exhaust duration and a wider lsa