Newbie question, can you have a stock fpr running with after market fpr at the same time? if you can, can there be any increase in power? did a search didnt' find any on this topic unless I miss something.

 

its a regulator.

if you have 2 regulators set at 50psi. the pressure will be 50psi

ex: one at 50 one at 20 fuel pressure will be 20..

u just wont be able to adjust higher then the stock FPR is set at

 

Common to do it with rising rate regulators. Mounting the RisingRate in the return down-stream of the stocker.
Its both the easiest way to install, and you keep stock drivability off boost. This is, ofcourse just rising rates for boosted applications.
Having two standard regulators on a NA engine doesnt make sense.

 

most aftermarket FPR's either modify the stock FPR or completely replace it, so no.