| I guess the most common objective of any emissions bypass system is to clean up the engine appearance by cutting down the number of hoses and vacuum lines under the hood. No matter the reason, there is always a price to be paid for removing anything that Nissan engineers decided was necessary. Too often, people who encourage removing emission control devices don't do a thorough enough research on the possible adverse effects. I commend the author for having done a pretty good job on his write-up and offer some additional comments. Here are a few things to think about if using any CC bypass systems. 1. One benefit of the CC system is it helps keep the fuel from going stale. A fuel tank that maintains pressure and minimizes evaporative losses will keep fuel fresher longer. Use of a bleeder might help as well as using fuel additives. In general you will be better off with a functioning system on a car in storage. 2. When the gas tank is vented to the atmosphere, there is increased risk of condensation and fuel contamination in the fuel tank. Condensation can cause rust and water to contaminate the fuel and increases the risk of having the gas tank fail due to rust through. I have often seen this in older cars before CC systems came into use. 3. There appears to be a mistaken impression that connecting the vacuum line from the balance tube to the line going to the throttle body will have a zero effect because both are vacuum lines. The vacuum line going to the throttle body does not tap manifold vacuum. It taps into the intake just forward of the throttle plate. That port is vented to the atmosphere at idle and then creates vacuum using the venturi effect as the throttle plate opens. Connecting the two at idle will be the same as creating a vacuum leak at the balance tube. The line from the balance tube goes to the CC constant purge orifice which is a calibrated vacuum leak similar to the PCV valve. The engine is designed to operate with a precise amount of vacuum leak from both these sources. So plugging the balance tube line would technically also be incorrect. Under extreme temperature conditions, or on a poorly tuned engine, there could be an adverse effect on a smooth and stable idle. 4. Safety issue. Venting the gas tank to atmosphere may cause fuel fumes under some conditions. Fuel fumes in a confined space can be extremely dangerous (explosion risk). Mistaking an actual fuel leak for fuel tank venting might lead to neglecting a fuel leak and create a significant hazard. There is a value judgment to be made on these issues that will vary according to individual priorities. Each person needs to decide for themselves what is important.
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A few possible negatives about CC bypass systems. - 
