Exhaust Manifold

Pardon my language ladies and gentlemen....
But what in the holy F**k is the pipe coming off the exhaust manifold into a box connected to the air filter housing?? Also, how is there nothing on the internet about this mysterious, seemingly completely unnecessary pipe?? Anyway the reason I ask is because I threw an open cone filter on and ripped off everything else and now I want to replace the manifold with one that does not have this hole in it. ANY help would calm me down!! Haha thank you in advance.

87 Cherokee,4.0, 5spd

A pic would help. If it a big fat flexy one connecting to the front of the air cleaner, it's an air preheater. It warms the air leading into the your air filter to assist getting into closed loop.

It's considered part of the emissions system. You may fail smog testing with out. Some shops do seem to check for it on their visual inspection.

Yeah that's the one... It just doesn't make sense to me. Is this the only car in the universe that has this?!! I'm just lost as to what I'm supposed to do with it now that I have an open filter. And after all these years no one makes a manifold to fit that doesn't have the opening?

Ignore it.

Yeah, that's the preheater hose. When I took the manifold off my 88 to have the cracks welded, I got frustrated with the dumb thing and cut off the whole clamped-on housing deal that wraps around the manifold, and threw away the ancient collapsed hose connected to the air filter box. That was all fine and good until a year later when the (california) smog tech guy sent me home for missing emissions equipment. I bought $6 worth of 2" flexible preheater hose, connected it to the air box and cobbled together a janky "mount" on the manifold with some scrap tin and hose clamps.

On my return trip the smog guy took a brief look to see if there was a hose connected to the airbox, and never bothered to even see if the other end hooked up to anything. I could have left it dangling underneath the manifold. He knew it was bullshit old equipment, but at the same time he doesn't want to lose his license and I can't blame him.

Basically, ignore the pipe nipple thing coming off your manifold - it's just a super primitive heat collector for cold environs and doesn't effect anything if you leave it off (unless maybe you're in Alaska or something). Don't tear it off like I did; leave it in case you have to revert to OEM for visual inspection someday.

Thank you guys for clearing this up for me. I am in California so I will heed your advice!