My worst leaks were, in order:
- oil cooler thermostat gasket
- oil pressure sender crush washer
- VANOS solenoid o-rings
- one of the eccentric shaft sensor sealing elements
- upper timing case cover gaskets
Replaced every gasket and seal on the top of the engine - finally no more leaks. It's my opinion that all seals on this engine will leak so long as it has the stock (hot) thermostat.
Dye is really easy to use, cheap, and effective. Clean everything first with brake cleaner, add some dye, and drive. Will show up right away. If you're really concerned about the dye, use spray on foot powder - just spray it all over the outside of a clean engine, and new leaks are really easy to spot.