you can run wideband 02 sensors in each pipe if you wanted but that would get pricey, but if you are interested look at FJO racings products they have a wideband that can be daisy chained to run all 4 cylinders. or you could run 2 sensors 1 for each pair of cylinders on their own map, but monitoring EGT's would probably be the most economical way to do it. you can grip it and rip it and read the plugs but that gets riskier and is only cheaper if nothing goes boom.