Toyota Repair: 1986 toyota corolla, intake manifold gasket, toyota corolla

Question
Hey I got a 1986 toyota corolla, it's having a really hard time running in the heat.  It seems to be okay when it's cold and gets worse as the vehicle gets to running temp.  I was told it could be fuel pump (mechanical pump + carb system). Another person thought that it could be the EGR valve.  Put a vacuum pump on the egr and applied 20 inches of mercury... it didn't have an impact on how the car ran.  what happens is the car revs to about 1000 rpm then drops to 500 rpm... and so on until it stalls.  Any advice?

Answer
The EGR test should make the engine stall at idle, if there is no effect on the engine then the egr valve is not working and should be replaced, there were a lot of problems with these carburetors so I think that this ios where the problem may be, the only choice would be to replace it, also check for loose or disconnected vacuum lines or a air leak at the base of the carburetor, it could also be a leak at the intake manifold gasket but since it's temperature related it could also be fuel pressure related, try replacing the fuel pump first to see if it helps, it may be going into a vapor lock condition, this happens when the fuel in the fuel line or carburetor starts to vaporize, more fuel pressure may help this situation.