I think i might have found the oil-pressure problem (the oil-warning light was flickering on), there seemed to be a steady flow of oil out of what seems to be a pressure relief valve on the driver's side of the head, just below the cam cover (it's a hexagonal shaped thing about three inches long with a hole at the end and ribs near the base). Even at idle there was a small flow out of this, I can only imagine that under load (when the oil warning light came on) there must have been a decent bit more coming through and dropping the pressure. Anyone know anything about these and whether this could be the problem (it would seem logical and I have been having a leak that was difficult to track down)? Can these be rebuilt or repaired? Are they common to other T series engines (ie: can I go down the road and buy one that's suitable)? A few people have mentioned the relief-valve inside the oil-pump could be worn or stuck but I'm not sure if this could explain the oil-leak (though they could quite possibly be occuring together). Thanks for your help guys. Chris.