chevy k1500 4.3v6 thermostat housing

I had to replace the termostat housing since, it was warped. Then I replaced it with a cast iron one from the parts depot. So my question is what kind of sealant should I use to keep the gasket between the intake and the housing form leaking? I used permatex water inlet housing sealer and, it still seeps. I aslo checked the intake for cracks and have not seen any. Also I used a straight egde to make sure to intake is not warped either and it seems to be good. I use high temp rtv silicone. I have seen it happen where the new gasket is the stick on type, with a white peal off backing.
if not pealed it can cause a seep. It really shouldn't matter much which sealant you use since the gasket is the part that should be sealing. If you don't properly clean both surfaces before you apply the sealant, you'll get the same type of leaks. Try using sand paper to rough up the surface after cleaning it and finishing it off with a swipe of alcohol to remove any left over grease. Also, don't be generous with the sealant, it should only be used sparingly to fill in minor imperfections, let the gasket do it's job!Car Repair Talk's forum.