I also posted this in the volvo 760 section...

I am trying to get my 85 volvo 760 turbo to pass emissions, it failed with the old cat by just a little bit. When we bought a new cat it failed even worse, but with the old cat is almost passes. My question is, the cat we bought was about $150.00, the dealer has one for $350.00 and they say that the car needs a special 3 way cat, thats why the cheap ones are no good. Can anyone shed any light on this? Thanks.

HELLO, I CAN SHED SOME LIGHT. YES IT NEEDS TO BE A 3WAY CAT SO CALL THE PARTS STORE WHERE YOU BOUGHT IT FROM AND ASK. OFTEN THE CONVERTERS ARE REBUILT, LESS QUALITY THAN FROM OEM. ALSO BE SURE THAT YOU DRIVE THE CAR LONG ENOUGH TO GET THE ENG. HOT. IF YOU HAVE TO WAIT IN LINE FOR THE STICKER SHUT THE ENG OFF. ALSO BE SURE THE ENG RUNS WELL, NO MISFIRES, SOME CONVERTERS ARE NOT ROBUST ENOUGH TO WITHSTAND EVEN AN INTERMITANT MISFIRE....