Fuel Pressure too high!!!

[ms1780]

I have 97 psd that is running around 85psi of fuel pressure at the schrader valve. I used an actual fuel pressure gauge to check it, although the package did say not to use on diesel, but as far a I can tell fuel pressure is fuel pressure. When I rev it a little it pegs out the gauge. I am thinking my fpr may be bad, but not sure. Any suggestions are appreciated. Also a step by step on checking fuel pressure with a gauge. I just hooked up the hose to the schrader and started the truck, gauge bounced back and forth between 80 and 90 psi. I have a wvo conversion, but I don't think that should affect anything to do with fuel pressure. Mike