Kevin-
Kraig mentioned using a leather glove to protect it and "tap" it with a hammer.
Assuming you did that, maybe it's time to get a bit more aggressive. (I'm also assuming your shift lever is not a prestine looking piece.) Try this..........
1) Confirm that you've loosened the shift lever's set screw.
2) Spray up under shift lever with a good penetrant. (PB Blaster, Kroil, etc. [not WD-40]) Try to use one of the little red tubes to get up into the lever where it slides onto the splined shaft.
3) Using a short block of 2X4 as a "buffer" between your shift lever and hammer, put the block of wood over "hub" of the shift lever and give it a good whack or two.
4) Put down hammer & block of wood. Now grab shift lever out at it's end and try rocking it off. (side to side and up and down)
5) Repeat #3 and #4 until shift lever comes off.
Your goal in hitting it down is to loosen it, so as you hit it, try watching it for downward movement. You may have to try this, then let it rest for a couple days soaking it with more penetrant oil and then come back to it.
If you're really good with things like this, you
could try "playing" a lit torch over the hub of the shift lever, but this is sort of a last resort, because unless you
REALLY take your time and heat it from a decent distance, you're going to burn the chrome off the lever in an instant.
Try the above method for awhile and let us know what happened......
Scott-
All I know about Kohler breathers is listed in the second link Kraig posted.