Where is the vacuum modulator valve located on my transmission? Does it play a big part in transmission shifting gears?

I truly feel that my transmission is in good shape. So I am checking the Bowden /throttle cable and vacuum lines.

In addition, Gilly the white plastic bushing is it called shift linkage bushing? That shift linkage bushing doesn't seem to look like the one I have on my trans. Is it an upgrade design.

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