Hi everyone. I am installing a HHO system in my 2001 Toyota corolla. I have a PWM for it. The only thing I haven't purchased yet is an EFIE. My 02 sensor is on the exhaust manifold and is easy to get to. After reading about Map and Maf sensors on newer model cars I want to know if the EFIE for the 02 sensor is all I really need. Thanks for any advice , Jim in Calgary