My car is driving like crap lately and I took it into the service shop and they said I need a new 02 sensor $165+65 labor=230. Man thas a lot of money to fork over plus I need to replace my front brakes which is a nother 300. Anyway I think I can get the 02 sensor from BMA for $120 or so. How difficult is it to install on a 535i. I know the 535i 02 sensor is way more expensive than the other e34's. Also where can I get the best price on this part. I've been reading the archive that there is a NTK substitute? for like half the price? Any info would be great.