I recall one fellow on Renntech who tried to inspect his IMS bearing, but without locking things down properly, which resulted in a chain slip and therefore a timing issue.
Apparently the IMS flange and/or bolts can leak, which a tech might try to fix by taking all of the bolts out at once. And if things aren't locked down, this could result in the timing issue.
http://www.renntech.org/forums/index.php?showtopic=29492&hl=IMS+slip+timing
Probably a longshot, but it might be worth asking where the oil leak was and how they fixed it.