Clean both surfaces try using a block to sand lightly or a dye ginder (preferred) lay a bead of RTV on the block, smooth with your finger. Also make sure the sender is ok, and not leaking, and are you running an egr still? if so, don't bother with black, use RED RTV or delete egr, adn use black or GRAY, gray is VERY strong. lastly DON"T EVER use the tube of RTV included in the gasket set, go to the auto parts store and get a tube of GOOD rtv, I used carquest brand on mine, it is very good, a bit expensive but worth it.

 

A friend of mine used a center punch and put indents about an half inch apart on the block and intake and used some RTV and hasn't had a problem since.