[fongo]

Ghettopop! No problem. I had the same exact problem. People were telling me it was the timing, the 02 sensors, etc. Although these are possibilities, it turned out to be simpler than I thought. First, about the pics, for the 1st pic, the sensor underneath the upper intake is the ACT air temp sensor and for the 2nd pic its the ECT engine coolant sensor (next to the oil cap and distributor). I originally changed both of those suspecting that those were the problem. It turns out they weren;t.
All I did was pop the MAF mass air sensor, cleaned with intake;/carb cleaner gently thru the tiny thermocouple insisde, After soaking it, I let it dry and restored it ( I have a cold air induction MAC, so it was easy). I also put in a new PCV valve too. Boom!! the popping went away, no more backfiring, bad fuel mileage etc.
Try it! You'll be surprised, those little things fool you. I learned it after spending over $100 in new ACT and ECT sensors (alhtough they werent the problem, it was time to pop new ones anyway: I got 167K!). good luck!