Location for Fuel/Air Guage

[YamahaRider10]

Where is the best place to weld in the bung for the Air/Fuel gauge? I read just before the muffler but not sure if that's correct. I have an undertunnel setup that I came up with on my own. Pictures and or help would be great. Thanks in advance.

 

[YamahaRider10]

This is on a MPI Supercharged sled also.

 

[FLYBYU]

The last Nytro I did I put right before the muffler. But that was with stock muffler.