Does the stock oil pressure gauge location read pressure pre- or post-filter/cooler pressure? I would think it was post since the filter location is between the pump and the pressure port but I was not sure. I haven't seen the flow diagram on this engine yet. It is probably posted on mnet where I never go...

 

post-filter.

 

I see the oil filter bypass when it opens, then. I wasn't completely sure what I was seeing. I think I lost about 10psi adding an oil cooler. Pressure is still good, though.