Mostly 5 and 9. I've seen some 7's as well.
Another I think would be an 8w7.
No chance. If an Eight is introverted, it's got to be because they're Ni dominant (obviously with auxiliary Te, as ENTJs are more common as Eights, but for 8w9s INTJ is a common type). I really can't see how else it would work. When it comes to Eight, I basically think:
8w7: ENTJ > ESTJ > ENTP > ESTP > INTJ
8w9: INTJ > ENTJ > ESTJ > ENTP > ESTP
All other types I have an issue with.
I've tested 5 and 7w8 depending on my mood when I take the test. I see equal aspects of each of these in myself.
I have an ISTP relative who seems 3 9 and 8.
Could he simple be 9w8 with integration to 3? (he has had plenty of time to "grow into" the 3 integration). Is a 9 workaholic possible? A 9 who values material success? His demeanor certainly seems 9, and he can be aggressive when he feels the need to.
:???:
3w4, 6w5, 7w8, 8w7, 8w9.
Those are all bad fits, other than 6w5.
The ISTP is... talented, but lazy at best. Not the Badass Directing Blowhard Achiever.
JCF have nothing to do with laziness. As usual, you are wrong.
It has a lot to do with function placement. Functions do not have static definitions in and of themselves. An introvert who still values sensual pleasures focuses it a lot on his own sense of space and comfort. Se becomes more focused on preferred areas and skills instead of throwing out some hyper ballistic energy out into the world. Nor do they value everything everyone else does. All IPs are critics. They won't take the obvious path of achievement.