I understand that the 2.5 litre V6 is finicky in terms of oil pressure. I read somewhere within the CEG pages that one needs to ensure that the oil pressure is correct otherwise the chain will bang against the cover (rear). Heard of this? My car was making the same noise, and then I changed the oil and ensure that the OEM filter was tightened correctly.

Problem solved.

1995 Mercury Mystique GS Sport
2.5 Duratec
K&N Drop In
High-Flo exhaust
Tint

Bad things:
- clear coat flaking off!
- timing chain going
- idler pulley defunct
- rack and pinion going bleh
- Ford dealerships