I just received this manual on ebay:
2003 Ford F-150 Bi-Fuel CNG Engine/Emissions Diagnosis Manual Original
Paid about $20. It seems to have a lot of good troubleshooting information, but I've been under the weather for the past 1.5 weeks. When it warms up, I'll go through this. I don't recall if this gave the specifics for adjusting the fuel rail pressure, but I'll check it out. I know it does give the pressure range and what the resistance of the sensor should be.

The pressure regulator you sent the link for is identical on my truck. I've been running it on CNG lately, but when I went to fill up a couple days ago, I heard the loud pop when I lifted the handle valve. I have to think something in the pressure regulator is faulty. This truck is probably going to shorten my life by blowing me up one day, but I figured eventually we'll have the problem resovled.