Irregular fuel pressure

What would cause irregular fuel pressure when the engine is hot?

I noticed a lag of power when i floor it, only when the engine is hot (ran 195 degrees when i noticed the lag of power with a 180 thermostat) It was pretty warm here today, probably around 25-27 degrees Celsius outside and i was running her hard, so the temperature doesn't surprise me (my car doesn't have a fan shroud).

I had a fuel problem last year and i replaced the Fuel pump with a new mechanical fuel pump. My fuel pressure gauge reads a mostly steady 4.5 -5 psi but drops down to 3 psi every now and then (idling in my driveway). what could cause this?

Below are some specs of my car:

My barracuda has a warmed over 360 with a edelbrock 650 cfm carb backed by a 727. I have a 1 inch spacer between the intake to insulate the carb from heat. fuel tank looks brand new and so does the fuel sending unit, fuel filter is new and shows clean and clear.

My Timing is set at around 16 initial and i believe 35 total with not exceeding 50-52 with the vacuum advance all in. (don't think it is a timing issue since the car runs great when cold and starts easy even when it is hot)

Any ideas...?