i saved myself the headache of making one myself and bought this http://www.boostpro.net/prodtester.html (scroll down to the evo tester).

That looks like a convenient option, but I only see it offered in 3" "for the evo." Correct me if I'm wrong, but don't we need 2.5"?

Yes, we do need a 2.5 inch, I made a boost leak tester in 20 mins. Just go to Menards, and buy a coupler, which comes with 2 clamps, and then just try to fit different pvc fittings in the coupleer until you get what you need, it takes a little testing because not all the fittings fit into the coupler, and after that, just drill a hole in the cap, and jb weld a rubber valve stem(from walmart) into the cap. And then just attach to turbo inlet, and pressurize! pretty simple....