Those are the air tubes attached to the smog pump that screw into the back of the heads and inject air into the exhaust. Ford calls this the Thermactor system. Without this system you will get higher HC readings in general as the air is supposed to allow unburned HC in the exhaust to get burned up before hitting the cats.
A really well tuned motor won't really need this, heck I have heard of someone with a GMC truck who had a chip burned etc and ran emmissions numbers way better than stock without cats or a smog pump.
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