the only way you will crack one of these is if for example you happen to be running some ungoddly amount of boost and oh say a heavy methynol injection kit combined with hitting the rev limiter and getting a freak back fire ingniting the meth and turning the intake manifold into a cumbustion chamber......not that I have seen anything like this happen

Anyways, yes the insides are different. On my miata I sand blasted the inside to make it better and now its pretty damn good. Even as it is normally its still a big power booster on big turbo cars.

I have never heard of a problem with #3 going lean. The real problem was holes in the casting causing vacum leaks. I have only come across one with this problem. Every one I have received in the last while has been fine