Originally Posted by Brian Carlton

If it's leaking into the intake side (most likely), then you can pull the crossover tube and the riser from the turbo. It will be wet with oil. With consumption at 1 quart per 1000, the oil won't be that obvious.......maybe a light coating. It's difficult to separate oil consumption by the turbo and normal blowby oil from the crankcase on the 603 because they both originate from the same place. But, if you have very low blowby, and you have oil residue in the crossover and the turbo outlet, I'd bet a dollar that the turbo seals are the culprit. My '86 has this issue right now........consumption at about 1 quart every 2K. This one shows signs of oil residue on the turbo and the external tube from the turbo.

The engine originated in 1990 and had problems right through '93 IIRC. So, it's not possible that the engine came from the factory with updated rods.