I guess I'll take the arguementative side. Leave the emmsions and make sure they are properly connected. Yes, they are ugly, yes they are a pain in the ass to work around, but they do work, serve a purpose, and you'll gain nothing by deleting them other than maybe a bit easier to work on when the time comes.
You'll also be suprized to find that when you take all those emmisions off, you will lose a bit of mpg, not gain any. Maybe only 1/2 to 1 mpg, but still a loss.
Also, as far as the visual inspection, it's just as important as the sniffer test. Things like a heat riser tube... A vehicle is at it's dirtiest when it's cold and not very efficent leaving unspent HC's and CO's into the air. Your vehicle isn't tested cold or it would likely fail. The heat riser helps eliminate the smog until the motor is warmed up by putting warmer air into the intake. Think of all the short trips people make that never even gets the motor completely warmed up. Also, the Evap canister... it does recover fumes that are not even measured. You can pass the sniffer test flying colors without an Evap canister, but if it's not there you are polluting the air. NOx, (Oxides of Nitrogen) also are not measured in the sniffer test and many of the visual emmisions help eliminate NOx. Things like Temperature Vacuum switches which will stop timing vac advance until the motor is warmed up and why it's important to have your vac hose routing done properly.
Now days, computers take care of all of these things. Many are not aware, if you computer controlled vechile doesn't get warmed up you'll get ****** mpg because the Temp sensor keeps computers from going into a full closed loop mode and tuning your motor for maximum efficiency and performance.
