Two warning signs of blown head gaskets could show a little water in your oil, you can check your dip stick and u would see a sheen, another way is removing your radiator cap and looking down. You can often see debris of a head gasket floating
having a fine car that is slow is like having a hot girlfriend that won't put out!
just a thought. if the cap doesnt seal properly it will let the water boil easier. when your system stays pressurized it is harder to boil the water. but without the required pressure the water will boil faster. if this makes sense?