It is a drain tube for the pan housing the heater core. If the heater core leaks it will go out that pipe instead of inside your car.
hose pipes, rubber sheets, and cord rings
You could just need to flush our your coolant pipes. Detach both hoses leading to passenger side firewall and spray into one of the pipes with a hose. It will come out the other pipe. This solved my problem in my '91 Ranger.
Water pipes may be covered with foam rubber to stop condensation dripping from the surface of cold water pipes in warm and damp climates, and to insulate hot water pipes so the water in them does not cool while flowing from the hot water tank to the faucet,
We use foam rubber to stop condesation of water from the surface of pipe.
A lot of heater cores on newer cars can be replaced from inside the engine compartment - much easier than spelunking up under the dash. Look at the firewall on the passenger side and determine where the heater hoses ( a pair of rubber hoses about 2" in diameter - one feed and one return) connect to the heater core. Most heater cores have the feed and return pipes protruding from the firewall. See if there is a panel that is removable from the firewall side - you might just get lucky. I am doing one of these in the next few days so we'll see just how hard it is.
With rubber or circular foam that you can by from any hardware store
I have a 2003 Grand Prix GT and the AC recharge port is right behind the motor on the firewall. Look for the silver pipes coming out of the firewall right near the middle. You will see the recharge port on one of the pipes there.
People who know about it prefer new plastics such as PEX or CPVC, not rubber.
In most Ford pickups you will find 2, 3/4 rubber pipes about 6" apart coming out the engine side of firewall. One will usually go to water pump or near it on the block, the other will go the rear of the block.
There are numerous vacuum pipes in your engine bay, They are thin plastic pipes about 1mm in diameter, and usually are attached to softer rubber, right angle connectors.
A person needs to have the diagram of all the parts in a vehicle while owning it. A person can get a diagram of the water pipes in this car by purchasing the maintenance manual sold at most auto shops.
On the front passenger side interior of the car, where the passenger's left foot would be, there's a plastic panel there that is attached to the main center console. Pull it off: it's held by a velcro type thing. You should see 2 pipes: those pipes connect to the heater core. There are 2 plastic clips: 1 on each pipe. unclip each clip. Make sure ALL radiator fluid is flushed and have PLENTY of towels and/or a drip pan inside the car. Be careful not to damage those pipes as they are aluminum. Pull the pipes down out of the core; it will get messy. Pull the core right out and replace. Do not lose the rubber gaskets and the plastic gaskets! Installation is reverse of removal. Good luck!