Fire_at_Will,
What kind of Mags are you using with your 1911? My LLamma had a simular problem, and some good mags solved it. I personally would recommend some of the Chip McCormick mags, as that is what I've used with great success, but any of the good pistolsmith guys that make mags, such as Bear, Wilson, Ect, put out some decent mags. Buy one an try your pistol with it, if it works then ya know that was yer problem, if it don't then you are stuck with a pretty good mag (more mag's are always good), and have to move on in your truobleshooting process.
Polishing of the feed ramp helps with minor feed problems, but is mostly done for increased reliability, and it is best done by a pro, as it is REAL easy to mess up the angle of the dangle causing worse problems.
Lastly you could try a stronger recoil spring, but I doubt that is the problem, as if it was you would be having the same feed problems during hand cycling of the action. (of course that assumes that you are jerking the slide back VIOLENTLY and releasing it at the full stroke, to simulate a firing cycle)
hope this helps