You need to CLEAN the intake up real good where the gaskets fit against it. Then make SURE that the intake is NOT PITTED, If intake is real smooth then there is no reason to replace it. Just replace the gaskets.
Your intake manifold gasket needs to be replaced.
A bad gasket can cause the air fuel mixture to enter the coolant stream, and cause bubbles in the overflow bottle. The gasket needs to be replaced.
Irratic idling condition is indication of intake/inlet manifold gasket leak. Change gasket immediately. This particularly applies to EFI engines. Newaz.
It is on the valve cover that's pressed against the firewall. The upper intake needs to come off to get to it, and the gasket on the uppert intake (plenium) will likely be replaced. Be sure to check the line running to the pcv for roting.
bad gasket. needs replaced
head gasket leak or thermostate needs to be replaced
An old gasket that needs to be replaced.
Your head gasket is shot and needs to be replaced
That narrows down which head needs a gasket or which side of intake needs a gasket. Check your oil for signs of water in pan.
replace it
check your oil to see if you have coolant in it. if you do your intake gasket needs changed.
The head gasket has blown and needs to be replaced.