If the ABS is periodic, I'd suspect the OVP. I'd also check the charging. It's possible your voltage regulators brushes are getting short, but usually when this happens you get an ABS and an SRS light concurrently.

There will be more opinions on this I'm sure.

Check out Doc's and Steve B's thoughts in this thread:

http://www.peachparts.com/shopforum/showthread.php?threadid=45977&highlight=ABS