What is the typical range of a TBI afpr?

I modified the stock fuel pressure regulator to make it adjustable and I'm not getting much of a change in pressure. Originally, I had ~11 psi. After modifying the regulator and all but maxing it out (judging by the tab seen in the housing opening) I'm only getting ~11.5 psi.

Does the regulator spring have to be changed to something stiffer to see any larger changes in pressure? BTW - The TBI was just rebuilt, incl the regulator diaphram.

 

I see 10-20 psi advertised for some aftermarket AFPR's. Can anyone verify this is possible w/ the stock spring by simply making the stock regulator adjustable?

 

In addiction to the AFPR I got a stiffer then stock FP spring from xtremefi that cant even hold 18psi under accelleration.

Ill have the 20psi spring from Top down solution installed soon.

I never tried but doubt you can get over 13psi under load with the stock FP spring. (apperently stock tbi Fuel pump doesent pump more then 14psi either)

Definally set the adequate fuel changes in the bin for the higher FP.