Use studs instead of bolts (takes care of the problem Dave H was referring to) and RTV on the gasket does seem to help. Also make sure there isn't a leak somewhere else. I was cursing up a storm when I thought my drain line was leaking, until I calmed down enough to realize there was a small trickle of oil coming out of the feed line on top, making it's way down the turbo, and then running down the drain line.