two 2.25" pipes merged into one 3" pipe? Sounds like a bottleneck to me. I still think I'd do a camshaft, too. You'll lose a little boost with the cam usually. What cam do you want to go with? Figure into the costs... cam, pushrods and springs. Installation costs tally into the cost unless you can do the work yourself. The headers just seem like a good start for a decent price since you're going to need them eventually.