What concerns me is the size of the port opening in the gasket , how can the eddy/906 heads use the same gasket as the larger flowing heads.

I placed the old header gasket i had from the eddy heads up against the ex ports on the -13s , there waayyyy smaller , this gasket was from TTI when i bought the 1 7/8 headers a couple years ago , so i would think it's the same gasket that is supplied with the 2 /18th step headers , if so i think i got a problem , as the ports in the headers are gonna be a fair size smaller too.