I was looking at the bassani headers but it seems that they leak a lot. I don't want to take a chance at making a problem if the headers arn't realy worth it in the first place.
*** Nevermind what I said below. I just noticed you have an 04 COBRA.
I did not see gears on your list. Look at 3.9 or 4.1. Easy to correct for with your Diablo Predator. Since you have an aftermarket TB, you could couple it with a new plenum. Also, maybe a Meziere electric water pump.
That is about the only easy ones I can think of that are not on your list.