6.9 came from the factory with umbrella seals on the exhaust, they went to positive type seals on the exhause on the 7.3 from teh factory, but then soon found that they did not allow for enough lubrication on the exhaust valve guides ( the intake will naturally have a bit of vacuum so will draw some oil in past the positive seal to lubricate the guide, but the exhause is under pressure and pushes it out so when they put positivre seals on the exhaust did not allow for enough lubrication and the things would eat exhaust guides.) all replacement gasket sets now contain umbrella seals for BOTH engines as an*upgrade* , although when I built my engine , I installed positive seals on all teh valves , knowing that it was getting synthetic oil right after break in so I knew the valves would be getting better lubrication even with the less amount getting to them ( so far so good, with 70k miles on the oil in it, the oils is still in good shape and it's consuming at a rate of 1 gal per 5k miles which would be the same as not having to add any between changes for most folks doing changes at 3-5k miles