According to the article here:
http://leetwanker.homeip.net/TPITuning.pdf

Fuel pressure should drop 1 psi for every 2" of vacuum. Therefore, since my FP w/ engine off is 42psi, when at idle, it should go down to about 33psi (assuming 18" of vacuum)? My idling FP is around 38psi, so maybe my fuel pressure regulator is bad? After 30 mins (with key on, engine off), my FP drops from 42 to about 26psi.

I am in the process of putting the car back together but I'll kick myself in the face if I put it all back together again and then have to pull it apart AGAIN to swap the regulator. I still can't get a good answer what the best one out there is, you get 100 different answers.

Jeff

 

my car does about the samething and it runs fine. but if you have the money do an afpr.

 

Try checking the FP with the engine running and no vacuum applied rather than engine not running.

 

dude your perfectly fine if you can hold 26psi for 30 mins i want ur fpr cuz mine was messed serious when i got the car it held 1 psi for 2 min now it holds 14-18psi for about 15 min and that is **** but it still runs great