If yours is like mine then you'll need to have the thing machined. The header tubes were not flush with the flanges and make it near impossible to get a good seal even with a good gasket. I couldn't reuse the stock metal gasket because the tube portruded so far. I haven't yet noticed any major leaks and the cost and time at this point isn't worth it for me to have it machined but I'm sure it will eventually. I kinda wish I'd gone with the FS one now.
The focus hacks instructions say to reuse the stock metal gasket if possible but I couldn't because the tubes weren't flush and the stock gasket wasn't big enought to make up for it. Kinda crappy if you ask me.