1) What is the "IQA" number on the injectors?..... Injector quantity adjustment. Whenever an injector is replaced, or to make corrections to the existing injector IQA data stored in the pcm, this number has to be programmed into the pcm for a particular cylinder. 2) What symptoms may occur if the code is not programmed in to the pcm?......Rough running or poor idle quality, and possibly no symptoms at all (depends if the flow rate is relatively close in the new injector compared to the old one). 3) Any other issues if not done right?......PCM can limit the vehicle to 55 mph and derate power by 30%. 4) is there an inertia switch as in older models?...... Yes, its in the side panel of the dash on the passenger side. 5) Just push the button on the switch and it'll reset and start, right?.........NO, theres a message on the instrument cluster that must be reset, and the key must be cycled off, then on before it'll start. 6) is there any difference in the egr cooler?...... Yes, if theres a failure, complete replacement is not necessary, it has a replacement cartridge. There is also 2 egr cooler "passages".