So I recently replaced the battery on my 2007 Mazda 6 (3.0 engine). A day or two later I got a ďrunning leanĒ code. Didnít have time to fix myself so took to my mechanic. He found the intake boot cracked close to the MAF sensor. He relaxed the boot, code gone but idle still slightly rough. Noticing a growl when I accelerate. Mechanic (who is an honest guy) says he thinks I may need a new catalytic converter but since I only plan on having the car another 6 months itís not a big deal if I donít replace. I drive for work and canít afford to have a major breakdown. Isle RPMs around 750. When itís idling it almost feels like a slight sputtering from the exhaust. Any help would be greatly appreciated.