Delcos are expensive and very hard to find other then a GM dealer
I just purchased an STP also and will install this weekend only because my Purolater cannot be found. Advance Auto has a invetory problem, too many Purolater filters have empty slots on the shelf. Anyway, the STP does not seem as well constructed, I miss the metal frame on the STP especially for such a long air filter as mine is. Filtering media seems good. Just not a sturdy looking as it bends if you hold it out whereas the metal frame of the Purolater keeps it straight. Probably no difference once installed.
I have taken to taping the air filter box with A/C foil tape to see if this will reduce my silicon count on oil analysis. Will see in several months if this has had an affect.