1988 Buick LeSabre, PLEASE HELP

We are having some problem with our 1988 Buick LeSabre with 113,000 miles on it. Let me start explaining the problems we are having, first, we took the vehicle to have it tested and two problem were detected, both were sensors, the first one was MAF Sensor, second one was EGR Valve. We replaced both of them, and the problem still exists. The problem is that we will start of the car, attempt to put the car in Drive, press on the accelerator and car goes DEAD. The car will restart, however it will die again. Then the following time it will start and i will have to keep my foot on the accelerator as I am putting the car in drive and peel off, then pray we do not get stopped by lights. However, when the car gets very hot from the summer weather it wont let me get beyond starting the car and pressing the accelerator, it dies the mind it start. Can you please help, we have one vehicle, we run a business and we have 3 children. Thank You, Stacey Goff