TB spacer, cold air kit, pulley's, long tubes, nitrous, and boost. But they really don't respond well to boost. Engine swap would be ideal.
what I said at the end of my post.For the cost you of doing the above you would have funded a ls based swap and have a better platform.
What kind of power are you looking to make? If your looking for around 350 hp you would be better just doing a swap.