Under the "don't do what I did" or "I should follow my own advice" headings!
I recently bought a SKP brand secondary air pump and check valve to replace the noisy original air pump (470,000 km.) Everything looked pretty good but it turned out the SKP air pump did not pump enough air to open the SKP check valve. After about 3 hrs. of messing around on a 1/2 hour job, I found that BOTH were at fault. The original air pump could open the SKP check valve but only about 1/2 way and the SKP air pump could only open the original check valve a tiny bit! What a bunch of crap! btw you can only activate the air pump in INPA with the engine running.