That pipe runs from exhaust manifold stove shroud. It preheats air to the air box for quicker warm ups or at least that is the theory.

You would be wise to leave it as is.

Even wiser yet, to take a 5/8 inch square block of something i.e. plastic or wood and place it in the air box flap mechanism.

The mechanism unsnaps from the whole box so you can get it into your hands. You remove the bogus brass thermostat and place the block under the spring-loaded plunger.

This holds the flap over the hot air port and keeps it closed off. This will prevent the overheating of the expensive Air Mass Meter.

It has occurred to me that if you lose one of those, you wipe out any of the gas savings that that apparatus saved you over several years of warm-ups. IMHO, the AMM self tunes all the time to the 0-2 sensor anyway.

The thermostat is truly a trick or treats deal to sell parts!
Happy Halloween
Phil