i heard it just blocks one fo the ports. has any1 tried to modify there stock gasket into doing this?

 

block a port? no it does something totally different. the purpose of the gasket is that it acts as a thermal insulator...reducing the heat transfer from the cylinder head to the intake manifold...thus keeping the intake charge cool. we also make a gasket kit but ours is 3/8 inch thick and comes with more hardware and is dyno proven.
http://www.defcon-racing.com/phenolicspacer.html

 

pretty nice, how much is yours? where is the dyno charts?

 

The "blocking off" you are referring to..

I think you need to cut some of the gasket, for coolant flow..depending on which head/mani you have