That is a horribly ugly vacuum modulator. Actually, when people have shifting problems on the 3 speed, this is probably the first thing that they replace, and this may be a good time to replace yours. Make sure you get a similar one - purple stripe - as the stripe colors dictate when/how the car shifts. In order to remove the modulator you need a special (very thin) wrench to do it. I forget the thickness of it - it is posted on the forum. The metal vacuum pipe is not part of the modulator.
'91 Tracker 8V, 1.6L, 5 sp, 4wd, 2dr, conv, CAMI, horribly rusty
'97 Suzuki Vitara 8v, parts car - worth its weight in gold.....
'61 NSU Quickly - 150mpg