| Do you mean the top?
That is the doomaflot sensor, it measures the amount of HD products that are being using in the bike, if you have the corrrect amount of oil, if it is HD brand, what gas you are using to see if it's the correct type to maintain the warranty.
The sensor on the top of the manifold is the MAP or manifold pressure Sensor and is used by the bike to set timing based on pressure reading from the manifold.
If it stops working your bike runs like crap...
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00 Heritage S&S 124 | 
We plan to meet next week to talk about planning a strategy session to discuss the next step towards forming a consensus to start the development of the rough draft for the implementation of our intention to develop a plan. 
