First before you put anything in your engine seal off the rear of the intake. This is hillbilly but it works. Take some carb cleaner and completely clean aal the gunk off of the rear seal area. Then take some silicone blue and glob it into and on to the crach where the rear intake seal goes. Be very genereous. Let the truck set for a day and it will stop the intake leak.. Many people mistake this kind of leak for a rear main seal leak. If you have a rear main leak use the gold eagle brand "engine sealer". It will swell the seals up instead of dumping garbage into your engine. I see no way how any engine sealer can cause head gaskets to blow.