Stock adjustable fuel pres. regulator?

Just wondering if there is a stock adjustable fuel pressure regulator you can order, or if it is possible to convert a stock regulator to be adjustable? Just went to put a Kirban AFPR on the car, and noticed a threaded screw going into my stock regulator. Seems like this would make it adjustable, is this something I just haven't seen before...or what?

Here's a pic of the stock regulator, sorry for the quality...my good digi cam is in the other car.

hrm well damn i had always assumed it had the stock fpr on there. Well I'm going to go take a closer look, see if it has any part numbers on it or anything. Thanks both of you!