1970 monte carlo cutting back I have changed everything HELP!!!!!!!!!!

i need help my car is cutting back like its starving for gas to make a long 2 weeks of trouble shooting short i was driving one day and the faster i went on the highway from 55 to 60 it was cutting back so i took it to the shop and changed the intake gasket , now it cuts off if i give it alot of gas when i come to a stop, but it cranks right back up first try. I have changed my fuel sending unit,fuel pump distributor, accel wires acdelco plugs, blew out the lines just bought the carb in feb took it apart looks clean it still acts like its starving for gas even when we swapped the carbs i dont know what else to do the mechanic doesnt know what to do what else could it be? HELP  

disconnect the coil power wire... so the engine will not start of spark... when you crank it...

disconnect the fuel line at the carb.... push a piece of fuel hose over the open end of the fuel line.. run it into a plastic gallon jug...

have somebody crank the motor...  while you hold the fuel line in the plastic bottle .... it should have full pulses of gas into the bottle... if they get less and less after the first few ... you have found the problem..   you should get over a pint of fuel in 10 seconds of cranking...

i have found cars with fuel problems... that the fuel lines were smashed flat... jack stands..  floor jack damage, rocks smashing the fuel lines...   fuel lines clogged with rust...  dirt...   strainers on the end of the fuel sending unit pick up tube  totally clogged or missing...   with the strainer missing...  it will have problems suctioning the fuel up as it sloshes around...


i have also found carbs with blocked fuel inlets... where debris has lodged in the inlet..  

check the fuel pump push rod and make sure it is not worn out or ground down by the cam I saw this in a 305 that sat for a while! the rod stuck in the block from sludge formation and the cam was just barely touching it.  

You said you changed the intake gaskets some times on an aluminum intake if you have leaks at the intake or carb you can start the car and let it run while you spray small amounts of carb cleaner near the gaskets/carb base if the engine pitch changes you found your leak if you have one. DON"T SPRAY ANY ON HEADERS THIS IS FLAMMABLE!!!! and of course your best bet is to start when the engine is cold good luck!