ok so i have a problem of lean misfire from 1000-1700 rpms. anyway i replaced tps, temp sensor, maf, etc etc. so finally yesterday my mechanic hooked up a testor to the computer to test my 02 sensors and sure enough one of them was fluctuating (like it should be) but the other one wasnt. so i replaced both.....now the one that wasnt fluctuating IS fluctuating, but not as much as it should be.....not as much as the other one is......what could this mean? what else could it be? thanks