Do the AC hose thing as described above. Use a liquid filled o-30 PSI gauge and have your hose long enough to run it out the hood and through the door at the hood corner. I check mine at idle and do a WOT occasionally. I store mine in the cab in a Ziplock bag. I have checked many 24 valve trucks for fuel pressure while filling up at the gas pumps and we get to talking about our trucks. I usually take the time to show them the small event at ignition on,the 25 second event at ''bumping'' the starter, and the idle pressure.
The TDR is always mentioned as the source of this information.