i had a similar problem with mine (98 ssei), mine had a lot of sludge in my motor. when it got hot it would break down the sludge into a really thick liquid and clog my p/u tube... plus my pickup tube screen had only a quarter size hole to pick up oil from all the neglect of the previous owner ...

figured it out the vacuum line from the map sensors was broke in half, and for the vents, the main feed to the hvac (pink hose) it was clogged,

im new here and just bought a 98 ssei for $700...

my boost gauge is not showing any boost, and not sure if this is related to it but my vents are not switching either...

does any know how the boost gauge on the cluster works..(ie vacuum or electric), and whats the best way to start the diagnosis...