[RICK LAKE]

FatBoy Paul Try the simplest way first. Take the mechanial pump out of the loop. road test the car and do the same test for fuel pressure. Have the pressure at 6 psi. If the car doesn't change and the pressure is still dropping more than 3 psi we need to look at the supply system and pickup in the tank.
I know that most cobras came with a 3/8" and 5/16" supply line for a carb car and mechanical fuel pumnp on the motor. The carb was only about 750-780cfm. Today 1,100- 1,300 cfm carbs are out there. Unless you are running a pump in the fuel tank, I see a couple of problems,
Under hard accel the fuel is being pushed to the back wall of the tank. If you are around or under 1/2" a tank of fuel the pickup may be sucking air/fuel combo. This doesn't work to well for a motor and lean condition happens. If under normal driving this is not happening, fill the tank to 3/4 full and try again the hard accel. If no problem happens the issue is the pickup in the tank. I have had to change my tank and rework the baffles. I can't run lower than half a tank of gas without having the same problem as you in high "G" turns or accelleration. If there is no change the next thing is to look at the fuel filter for possible clogging and partial flow. The newer gas out with 10% ethenol is eating any rubber hoses you have on the car. Very small pieces of the rubber are clogging up, filters jets, needles and seats of the carbs. This has happened to a couple of guys here this year.
If the electrical pump is not getting the job done, I doubt the mechanical will fair and better. The next thing would be to run a larger line from the pump in the back to the tank and repeat the drive. If car gets better you have your answer. If not start looking at the carb. Ps I run 1/2 line to my all my cars and 3/8" return line with a good fuel pressure regulator at 6.0-6.3 psi. This system never drops more than 1 psi at WOT. The other idea I have is the fuel is cooking in the lines. I would rap the supply line with a deflector tape and foam insulator. Last Question Does this problem happen only when the car is hot? and not when cold or warming up?? Rick L.