Hadn't planned on going less than the book says. Anyway, I got 613 ohms at the tightest setting, probably will just button it up after I replace those crappy choke ferrules with those fancy brass ones I just bought!

I believe it is a mistake born of early attempts to adjust.
If you simply loosen and replace screws and then adjust to a "lower" number.... you will not get to 500 ohms...so "go as low as you can "

Then folks removed the steel spacers (which works fine, just do not over tq the screws and use a drop of thread lock) and got it to go lower....500 was easy now, but hey I read to "go as low as you can, so look 460 ohms is that"

Or folks removed the steel spacer and cut the housing a bit, reused the spacer and now 500 ohms was easy but hey I read to "go as low as you can, so look 460 ohms is that"

But it was never intended to be set that low....it was set to 500 ohms OR as low as you can

My 2001 runs best at about 510 ohms, but darned if i did not try lower, all the way to about 460 ohms.

By all means, experiment with it...if it runs better at XXX ohms run it at XXX ohms just dont blindly set at "as low as you can"

Set it to 513 ohms and that's fine with me. Fiddling is fun...for a bit, then it becomes tedious. Lowest setting it would go was 486 without the brass liners. Did not tighten them down too tight, used blue loctite...just in case. Thanks again folks!