You could open those .021 holes up with the lifter bushings installed using a pin vise and turning the drill by hand. Probably need to go up about .020" at a time to reach whatever size your going for. Cleaning out the passage will be critical once finished of course. I would run a camera through the passage when finished to make sure they are absolutely clean. I have also carefully driven the bushings out, drilled larger holes in another location and driven them back in with the new hole exposed to the feed. Saves a couple hundred bucks for new bushings. But you will need to do a little touch-up hone on them once re-installed. Either way will work.
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