Running probs

Alright i finally got my car back up and running and im having an issue but im at my wits end so i wanted to see if anyone had any ideas....
318, mild cam, intake and 4 barrel carb
First off i rebuilt the carb eldy 600 checked float levels...
installed new fuel pump
and it runs BUT when i first start it if i look at the fuel filter it is laying horizontal and it is about half full and the car runs fine but after reving it or letting it idle for a few the level in the filter goes down till there is nothing in it and it is basically using whatever is coming through the lines and the car starts cutting out if i try to rev it. I have blown out the lines, tried a different fuel pump, unhooked the fuel line from the carb and ran it to a bucket and it seems to pump fine. The only theory i can come up with at this point is when i got the car the tank was rusted BAD so i put a new tank in it and it fixed the prob (Bout 10 years ago) but maybe the lines on the inside are closing up like arteries and they are not letting enough fuel through when it is hooked to the carb but when there isnt restriction (carb unhooked) it flows better? so im thinking at this point i might just run 3/8 lines from the tank to the motor.

But i should get it back tonight from the exhaust shop so ill see how it runs tonight.