Two things haven't been mentioned: (1) On what round does this nosediving occur? Top, middle, next to last - What? (It can make a difference.) (2) What magazine, or magazines, does this problem occur with? One, two, or all magazines?
Internet gunsmithing is always hard; sometimes it's impossible to correctly diagnose a problem without actually holding the gun in your hands and examining it. This said, I'll take a shot. (Yes, that's a pun!)
Sometimes polishing the feed ramp becomes more a part of the problem than part of the solution. (1) If there's too much of a, 'mirror shine' on some ramps a feeding problem will become exacerbated rather than solved. I've had guns where slightly roughing up the ramp with some extra-fine grit Emery cloth, along with a light coating of oil was all that was needed to finally straightened them out. (Too shiny a ramp - with too little friction between the bullet and the steel - actually gives a forward moving cartridge a choice of which direction it wants to head in.)
That leaves two other possible causes: (2) The front angle on your magazine follower is too low; but, with more than one magazine involved, this might not be it. (3) There might be too much of a gap between the top of the magazine, and the top of the magazine well. (This is a magazine well, upper dimension problem from which thousands of Glock Model 36's once suffered; and, I'm sure, from which some of them still do.)
How do you check for it? By inserting a small piece of heavy cardboard between the top of the magazine well, and the top of the magazine, itself. Shoot the pistol; and if the problem disappears then it's back to Kimber you have to go with the gun, and a full report. I hope it's something simple like only an upward adjustment on the front of the followers of only one or two magazines; but, via the Internet, it's impossible to know.
Before you go any further than this I suggest you mark each of the magazines involved with something like a, 'magic marker'; (Gun solvent will take the marks off.) and pay careful attention to what particular round, 'in the stack' takes a dive. Keep notes, too, just in case you need to correspond with Kimber. (Who, probably, isn't going to be happy to see, or hear about, that polished ramp.)
Best I can do for ya from within the depths of cyberspace!
NOTE: Just re:read your post. Did you say, 'All rounds'? ALL ROUNDS FROM ALL OF THE MAGAZINES! Take the bright polish off the feed ramp; and you should be fine. Do this progressively, a little at a time. Stop. Fire the gun, and test to see if the nosediving has disappeared. Make a final stop when the problem goes away; and don't polish your feed ramp, again - OK.
If this isn't it; (and, with a quality 1911 like a Kimber, I think that it is) then it's #3 above; and I've already told you what needs to be done, there, too.