make damn sure you have every little bit of silicone gasket off the block and down in the crevaces on the sides... take a pick or something and get it cleaned out..
i know that when i bought my FRPP performance gasket set it came with 2 sets of the pieces... one were longer than the other... its possible that maybe you got the wrong peices... but give every effort to get those installed.. there a pain, even the ones that "Fit" still seem alittle big. Goodluck