Iv'e had this problem for awhile now it's giving me a real tough time .so far there's no vac leaks car runs good I changed out the rear o2 censor any thoughts would be helpful thanks..

We need a little more info, like year miles NA/turbo and why you changed out the rear O2/did you replace it with OEM or generic. Are you using 87 octane or 91? What kind of mpg are you getting?

The P0422 = Main Catalyst Below Threshold (Bank 1)
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My name is Klaus and I am a V ♂ lv ♂ holic.

Klaus sorry for the lack of info,this is my daughters car and I'm trying to fix it while she runs around with it. So it has 93,545 miles, 2.4 turbo I changed it becuase I did a search on the code and this looked like the fix the car runs real good. I used a Bosh replacement and the car uses 87 octane. The light stayed off for a while and came back on again. I scan'd it and now I have a PO456. I reset the code and lets see if it returns. I'm going to start to change some small vaccume hoses. ??? pending