Originally Posted By: jonny-b
There could be a slight possibility, that it isn't the valve stem seals, right?
If not, you could start a car-doctor service on the web, if you are so certain about it being the valve stem seals(even though I think this is the most likely cause).
To state what the problem is, without seeing the car, is quite difficult, and most people know that several other things can play a role.
As I said, try this MMO that will cost you a couple of dollars first, and THEN, if it doesn't work, do the mechanical fix.
While this is true - it is a pretty well known fact that the early 90's 4.6 engines had bad valve seals. Couple that with the mileage of the vehicle - if it quacks like a duck, walks like a duck and looks like a duck . . .