I also have a Butler stroker kit and as low as 20psi oil pressure when the engine is really hot at idle (240°) for example after a long high rpm drive... most of the time (normal usage) the idle pressure will be 25-30psi since I switched to VR1 oil (5w50). It gave me about +5psi compared to the 10w40 I used before. I always use Wix filters, I think they give more psi than a K&N filter and they can handle the pressure.. never had a problem with one of them.
But at higher rpm's my engine will make more psi, for example 3000rpm at 220° oil temp is about 75psi (I use the 80psi pump). 45psi at 4000rpm isn't very much, but at least it's more than 10psi for every 1000rpm
I read that the Melling select pumps or the Butler one can give more pressure and more oil flow, about 6 gpm.