I have a 1990 gmc seirra 1500 4X4 with the 5.7 350 in it....im having trouble with it missing and backfiring thru the intake after it warms up...it runs fine cold....i 've replaced the plugs , wires , cap , button , and fuel filter and the fuel pump is about three yrs old...any ideas or experiences?

stuck egr valve would make it run crappy. In the old days we used to have a thermal spring and heat riser what closed a butterfly...these days we have a TPS throttle position sensor and thermo-time switch (not certain on this model) all these things after 2000 are still a learning curve for me too, the fact that once it warms up, gives you trouble leads me to question a temp sensors ability to tell your computer what the current operating temperature is. See if your EGR valve isn't clogged up with carbon and still activates correctly, then we will take a look at what thermal driven devices we can inspect...ok?