Recently I changed the oxygen sensor(late August)on my 86 300E , almost immediately noticed when I decelerate I hear back pressure from the cat. I figure the cat. probably has to be replaced(car has 193k mi. on it and also noticed that the metal is peeling). I don't smell rotten eggs or anything. My question is, once I change the cat. (did I wait to long?) do I now have to again replace the oxygen sensor?

------------------
Richie
1986 300E
tint windows
clear corners
euro headlights
16"chrome lorinsers RS90
soon to be 94/95 taillights