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Are you looking for the cannister purge valve or the cannister vent valve?
The purge valve is on top of the intake manifold on the right side near the distributor. The connector will have a pink and dk green/white wire going to it.
The paper clip icon above is for attaching images. Sorry but it's difficult not knowing what part you have. The information above is for the purge valve so apparently we're not talking about a purge valve at this point.
Take your time. I'll be around except for a period around 5 eastern for a while.
That part has nothing to do with an evap system on a 4.3 S truck. In addition to working on them over many years I also own one. . I'm not sure what issue you are chasing or what part you are trying to replace but if your issue is with the evap system, you've got the wrong part.
A po446 is not caused by a vent valve but usually either a stuck on purge valve or a failed fuel tank pressure sensor. It is for excessive vacuum in the fuel tank when none is commanded. The part shown is a purge valve just not the correct one for your vehicle. It is difficult without a scan tool reading the data however refer to the picture at the top of the page. They can fail intermittantly but if there is vacuum coming out of the valve when the electrical connector is disconnected... it is leaking internally and will cause a p0446.
Being honest, it is impossible for me to tell for sure what the problem is without reading the data and testing the circuits. THat being said, an internally leaking purge valve is the most common cause. I will tell you however that fuel pumps generally come with a new fuel tank pressure sensor and that is the second most common cause of a p0446. If the pump assembly was aftermarket, many of them use poor quality tank pressure sensors.