I have a 2001 Viggen coupe. Full synthetic (Mobil 1 0W-40) plus new filter at 5K without fail. Also always check to see if there are ANY leaks or oil films anywhere near the head, but mainly on the passenger side where it joins tte block and at the cam plug on the drivers side. ANY film indicates too much PCV pressure. There have been at least 3 TSBs on this issue. Additionally the B205 and B235 cars can run lean at full boost so make sure the engine software is current. This is what does in the pistons in the B235 engines. This could be the problem at higher altitudes. My MAF did develop a crack and it was replaced under the CPO warranty when they did the digital ignition cassette (DIC) recall.
Another cause can be the headbolts from the 1999-2002 era which were not torqued adequately at the factory thereby causing blown head gaskets. Have them retorqued or better yet get the new upgraded bolts. The new design bolt has cured this.
Viggens are nice cars, and it is the only SAAB that can come close the the saying born from jets due to the fierce midrange acceleration but I would never buy another SAAB since they are all sedans or psuedo wagons, you cannot feel the turbo push anymore, and they canned the hatchback. They did however cure the flexible flyer chassis of the first generation 9-3 ('99-2002).