Car is currently being diagnosed by my tuner or his mechanics. He discovered I had replaced the 02 with a Bosch(15730) sensor and strongly recommended that OEM should always be used when it comes to o2 sensor. Well I was going to buy an OEM but couldn't stand the rip off price of 250+ so thats why I got a Bosch. I'm sure I'm not the only one using a Bosch and other members here know how expensive the OEM piece is. The new Bosch 02 eliminated the po134 and now I just have to worry about PO172. I think I had PO172 with the OEM unit(but it was on its way out due to PO134) as well so its gotta be something else(fuel trims maybe?). Anyway I went and bought the OEM 02, ripped a hole in my wallet at the same time and will find out tomorrow if it really gets rid of PO172 code. If it was a bad o2 then wouldn't the car throw a code other than PO172?

Is PO172 a MAF code?
I even googled the causes for PO172 and people say it could be the maf sensor, injectors, dirty air filter, fuel pressure, vacuum leak