Monte Carlo 2003 3.4L Overheating

HELP ME PLEASE Monte Carlo 2003 3.4L Overheating
Bought the car with issue put presser tester on and could see and hear antifreeze leak on lower intake manifold gasket under throttle body.
Yes there was water in the oil. replaced gasket with felpro brand and just because I could I relapsed water pump thermostat and spark plugs. also oil change. NOW I opened bleeders and filed with coolant. pressure in radiator jumps instantly to bypass cap and bubbles in overflow bottle. cap tested at 15 psi. no heat out of heater in car and temp rises fast if under load. only get steam out of bleeder on water pump when engine running and oil looks clean. steam out of exhaust. WTF is the head gasket bad too.
HELP

I don't want to tear back down to do head gaskets unless I am sure that is the problem. I am now getting misfire cylinder 1 code.
drained cooling system and put flush kit in. flushed system and drained again. still getting presser in cooling system and cant get all air out. so I drained and removed lower and upper rad hoses. both heater hoses and have steam instantly coming from pipe to heater hose from engine block on a clod engine. so I removed serpentine belt in case water pump is pushing air though the cooling system. And still stem from pipe to heater core. Am I screwed is the only answer head gasket?

If the cooling system pressurizes in a matter of minutes, that is almost always a head gasket.

I don't want to tear back down to do head gaskets unless I am sure that is the problem. I am now getting misfire cylinder 1 code.
drained cooling system and put flush kit in. flushed system and drained again. still getting presser in cooling system and cant get all air out. so I drained and removed lower and upper rad hoses. both heater hoses and have steam instantly coming from pipe to heater hose from engine block on a clod engine. so I removed serpentine belt in case water pump is pushing air though the cooling system. And still stem from pipe to heater core. Am I screwed is the only answer head gasket?

Pressure test the cooling system and take the #1 plug out. Pump it up a couple times. Unplug the ignition module connectors to disable fuel and spark and crank the engine over and see if coolant is forced out of the plug hole. (might want to remove all 6 plugs) 2 ways in and you already did the lower intake gaskets. The water pump can't push air through the system by itself. The air is coming from combustion, most likely cylinder #1 seeing as how it misfires also.

If the cooling system pressurizes in a matter of minutes, that is almost always a head gasket.
Don't you mean in a matter of seconds here?

Ok number 1 compression test was 30 psi lower then all the others.
So I replaced the head gaskets job wasn't all that bad and instant results.
No over heating problem now. Thank you all.
HOWEVER resanator is bad and now i get right lien bank p0171 code.
The fuel gauge is all messed up will bad conection on sending unit affect fuel pump also?
AHHHAHHHHHHH.