I am wondering what is the differance in the two models? The specs. are the same on both. Model Displacement (cm³) Power(kW/HP) Weight (kg) STIHL 084 121.6 6.3/8.6 9.4 STIHL 088 121.6 6.4/8.6 9.9 Was it changed to meet emissions/EPA Regulations? Or is there major internal differences in the two powerheads?