Alright, well being that it is a prototype, I am assuming that the tubing used to make it is the inferior material, like that of a Megan Racing or OBX exhaust manifold. Not that this is bad, but it can be an issue if you plan you run excessive amounts of boost. Being you are boosting your Focus, I assume you will be running a low amount of PSI. This is a factor played into what manifold you need to run. Heat and wear over time will crack a manifold, but if you run enough PSI, is can make it crack much faster. How much PSI do you plan on running?