I remember seeing 4, 2 on each pipe, 1 before the cat, 1 after... real oem shows them on one of the pipes only... I am too lazy to jack the car up right now - can anyone tell me for sure?

Also, ebay has front and back lambdas.. do i necessarily need to replace the rear ones as well because I was told that the computer reads only the front ones (the rear are only used to rest the cat)? Thanks!!

ok ok.... just went into the garage and jacked it up..

http://static.bmwfans.info/images/epc/MTI4MDAzX3A=.png

Mine seems to only have two sensors before the cats (number sevens) on each pipe, however they are on the inside facing each other (under the gearbox); there are no number 8's.. is that normal?

come on, anybody??