Actually, I've heard intake spacers do pretty good for Machs..You will not see a huge difference, if any at all. I was just looking into them, and I was told by several people that they are a waste of the $65 or how ever many dollars they cost, and a waste of whatever time you put into putting them on. Intake/TB spacers probably do about as much as a Turbonator. But if you're pushing 500rwhp and running out of possible mods, go for it.
My advice, take it or leave it, is to save up for that tuner and gears. Those actually do make a difference.