There are 3 orifice sizes you can change to on the the AEM FPR; .100", .150", and .200". What this does is allow the fuel return to flow with a restriction or less of a restriction, depending on your fuel pump being used. If you don't have the right amount of flow back to the gas tank, after a harder throttle with too small of an orifice you can get a very rich and rough idle for a few seconds until everything normalizes. Just the opposite happens if the orifice is too large.
My question is this.......I have the Wahlbro 255 lph fuel pump and the AEM FPR comes with the .100" orifice already installed but I believe it is for the stock fuel pump but am not sure. Does anyone have any idea which orifice would be the correct one to use with the Wahlbro 255?

 

The same one. Don't change it.

 

I figured I would just leave it alone for now and see if I had any problems; But thought maybe someone else may know for sure if it needs to be changed or not.
Thanks Sideways.

 

I did not changed the orifice and did nice job with the walbro, and thge stock

 

thanks Juan.