PIMPIN F150

so i need some advice but first my truck is a 97 with a 4.6 with 160k miles on it so after few hours of truck sitting when i start up it misfires runs rough for about 30 seconds. i found out im getting coolant in my combustion chamber. i know this because after driving it for what ever time i park it i open the hood loosen the pressure cap for my reservoir slowly to release pressure and the next morning when i start my engine it runs perfectly fine. if i dont release pressure it will misfire untill coolant is burned off. i pulled the codes got a cylinder 1 and 4 misfire. my question is how do i determine if its a headgasket leak or a intake. this truck always had some small leak i could never find but could smell the coolant and finally one day the radiator tank finally gave and cracked and my truck overheated for a few seconds. and my luck was 300 miles away from home on a sunday. but replaced radiator made it back home everything fine then 2 weeks after now i have this issue. thanks for everyones help

Jbrew

Well, you shouldn't have to release pressure. That means your degas bottle cap has failed or needs to be cleaned or replaced.

It overheated, - that's not good, even for a second I'm afraid.

So, purchase a hydrocarbon test from auto zone or whatnot, confirm it's a gasket.

If it's a gasket and it being a 4.6L (dime a dozen), it's cheaper, faster just replacing the engine with a good used one.