some say to block the exhaust cross over port and some say not to..whats the difference?

 

This is something they did back before emissions even. The idea is to heat up your intake manifold so the fuel vaporizes better when its cold. Hence, therefor and forthwith it runs better when its cold. Nowadays its part of your smog equipment. If you need your egr to be working then the Exhaust gas recirculation comes from the cross over. Back to the intake heating. David vizard has pointed out that with an aluminum intake you don't need as much intake manifold heating unless you live in a cold climate region. So,...if you need your smog to work leave it open. If you have a cast iron intake and/or you live in a cold climate leave it open. The two previous statements are left to your own judgment.