I have a mild 496 stroker in a 74 cuda.  Since adding a new fuel line and pressure gauge, I've noticed that the pressure drops down to 1 or 2 psi and sometimes ZERO after the car has been running for 15 minutes or so.  (this is the first pressure gauge I've had on the car, so I don't know how long I've had this problem)  It will also happen after a short or long drive.  The car runs good and doesn't seem to be running out of fuel.  I've replaced the Carter mechanical with an electric Holley "Red" 7psi pump and I still have the same problem.  The thermostat is 160 degrees.  

Is this caused by too much heat under the hood?  Too much heat from my headers?  Should I insulate the fuel line as much as possible?  Any input would be appreciated.  Thanks.

More info...I have a 3/8" fuel sending unit going to the electric pump located at the fuel tank.  The fuel line 8AN braided from Jegs.  The sock on the sending unit is new and filter is an 8AN Russel located before the pump.  The line runs along the engine compartment into a Holley fuel regulator at the front of the engine compartment on the frame.  The line from the regulator goes up to the line feeding the carb.  The pressure gauge is at inlet of the line to the carb. 

It's always a good idea to have cool (temp) fuel, but since as you say it does'nt run out of gas during driving conditions. does it start hard after a long drive (maybe vapor locking) ? how about hard acceleration. If it doesn't do any of these things.

I would be looking at the guage. The rest of the fuel system sounds ok.

Denny

I would look at the gauge because 1 to 2 psi would definately cause a change in the way the car runs, especially when driving.  

try different pressure gauge to make sure you have a problem and it is not the gauge.