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.
We use foam rubber to stop condesation of water from the surface of pipe.
With rubber or circular foam that you can by from any hardware store
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,
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.
People who know about it prefer new plastics such as PEX or CPVC, not rubber.
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.
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.
Foam rubber tubes will protect them from cold.It would be helpful if you stated WHAT you want to protect them from !