Don't waste your money unless you can get rid of the pre-cats. You can't get rid of them if you need emission testing. Get an engine from the junk yard and get rid of it!My 2006 Mazda 6 3.0 V6 automatic is the biggest piece of shit I ever bought. I have 42,000 km and have had the following changed: transmission (put on tranny cooler after that!), fuel tank & sending unit, 1 pre-cat and other cat. Currently I have changed 2 O2 sensors and 2 more to change (idles like shit with no get up). The exhaust had to be re-worked because the bends were too sharp and flattened in front of main cat (worst exhaust design I have ever seen). The O2 sensors from Mazda are cheap. I am putting on NGK, NTK O2 sensors on. I would like to buy a different car, but I am currently not working, living off my savings from selling the condo, so I am trying to fix things to avoid pre-cat shit and semi-enjoy the car. My emissions test comes up in 6-8 months.