The stock crash did that for me. :(

Cold hard facts are you probably wont see any significant gains going from the nismo exhaust to any other aftermarket exhaust, unless you have other modifications.

True: The more you spend, the more you get

I believe from a cbe you won't get that much HP gains without a tune. Most people don't tune for simple Bolton's like cbe and cai but if you did, you can reclaim lost HP and possibly gain more HP and tq from the mods.
I think of it like swapping out HDDs on a computer, if you swap from a 1g ssd to a ssd 6g with sand force controllers and never install the sand force drivers, you will notice a speed increase but it isn't running to its full potential until you reprogram(install drivers) the computer to take advantage of the speed the newer hardware has to offer.