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#4: 02-06-2013, 08:13 AM
Title: Contributing V.P.
Location: Milwaukee
Car: 99 Legacy 2.5GT Toyota Supra 2jz/R154
Posts: 1,048
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BTW, the o2's are placed in front and in back of the second cat so that is the one the ECU checks the flow efficiency of. The first pre cat just helps burns so the second cat doesn't have to work as hard. Remember that if you have a cylinder misfire and let it go for a while you will destroy your cats. Same with running too rich, burning oil or coolant for extended periods of time.