from that website .. which size should i order? i have the buschur intake..and an evo green

2.5 or 3inch?

EDIT: im not sure im getting the way to do the test even after reading..does the boost leak tester connect at the turbo inlet itself? meaning i have to remove the whole intake pipe? if so what do i do with the upper intercooler hose that connects to the intake?

Or do i connect it to the end of the intake pipe instead of the filter?

 

The sizes posted on the site are inner diameter. You're going to have to figure it out. I depends on where you want to test. I use mine on the compressor cover.