I have a 92 Chevy S-10 Blazer 4.3 Vortec 4X4 W motor. I am having a problem with a loss of power. I had an issue with the fuel pump suddenly going out leaving me sit. Not knowing the issue I replaced the pickup coil, ignition moduel, bug, cap, plugs and wires. With no resolution I took the blazer to the shop and found it was 50 degrees off time and the fuel pump was bad. Ever since then I have had a drop in power. I have checked back pressure on the converter, have changed the TPS Sensor, have done a pressure check on the cylinders, have done a pressure check on fuel. I had my shop put it on test and found nothing wrong with emmisions, temp, injection, nothing. I have now noticed that for the first start of the day it is really hesitant to start and almost sounds like it is poping or backfiring a little bit in the intake. The backfire sound just started a couple of days ago. It will hesitate for a few seconds and then idle just fine. When I take off it has it's normal power that it use to have but while I am taking off the power will just all of the sudden drop and then it will not have the power again until I let it sit and cool down. Once it cools down like over night I start it up and the same thing happens again. I have run out of ideas that I know and need your help.