I just figured out what was causing my mysterious fuel pressure drop so take note so it won't cause you the grief it caused me! Would you believe it was not dropping at all. It seems that liquid filled fuel pressure gages are not recommended under the hood when exposed to heat! The "bourbon tube" that expands when the fuel pressure hits it, is connected to a spring that moves the gage needle in the positive direction. When a gage is filled with a liquid the heat causes the liquid to expand and collapse the "bourbon tube" causing the gage needle to move in the negative direction hence the falling fuel pressure. I used a liquid filled gage because they dampen the needle so it will not bounce under the mechanical fuel pressure spikes. My advice is to stay far away from liquid filled gages if you are putting them under the hood!