I have blazer that was running rough now it has quit running. Before it quit running Ireplace the egr value. Then hooked the computer I got a code for the O2 sensor and trottle body sensor. So replace them one at a time to see witch one was bad it still did not fix the problem it still ran like it was starving for fuel. So we replace the fuel pump. It still did not change the way it ran. We where told to try the temp sensor. Then the check engine light came on again the code at this time was random misfire so we replace the wires, plugs, cap and fuel filter. Still a random misfire code. We check the fuel pressure we had no fuel pressure.The pressure would go to the 62 psi but would drop off rapitly. The truck would still start. So we replace the fuel pressure regulator. The truck start for about 2 minutes and died. We had no fuel pressure still. So replace the fuel pumpagain and fuel tank pressure valves. We now have fuel pressure but the will not start. So it quit running after the fuel pressure regulator.