2002 Pontiac Grand Prix coolant leak internal, cylinder 1 misfire

Cylinder 1 misfire. Coolant was leaking by coolant temp sensor in lower intake (intake it's self not a gasket). Put coolant stop leak in it and the leak stopped. But it was drinking antifreeze as well. Took it down to head gaskets. Reading the valves 5 cylinders was getting antifreeze into them cylinder 1 was real bad both valves white. The other 4 cylinders 1 valve each was white and cylinder 6 was burning normal. Lower intake was good. Head gaskets look okay. Look being the key word. Both heads was cleaned and crack tested and he said they both are good. Now my question is do you think that there might be a chance that the lower intake is the culprit and if so have you seen it before