Although these are not always needed they come in very handy when you have little or no results in mpg. A scanner that reads fuel trims map mass air tps ect iat o2s and mil sec of time the inj is on spraying fuel this in time will give better success on those problem ones you may incur. If you transplant any components Iat or map mass air etc youll know very quickly wether the ecu is adding or taking away the fuel and how much. If you take too much fuel away the ecu will get wise and dump fuel leaving big pos numbers on fuel trims reset and start over gradually take away and it`ll remain happy and cut fuel small neg numbers and the mpg will begin to rise. I use a MAC taskmaster scanner and it serves me well. Any scanner that reads these things and parameters will work fine. Also the vacum checks are very important but after you get use to reading the scanner and understanding whats happening you can tell if theres a vacum leak think of the scanner as a doctors stethescope or heart monitor. Hope this helps Dan gadgetman Mo.
