My car failed a Md. emissions inspection this week (high HC and NO). The car still has all the factory emissions stuff as well as the dual cats. As a "worst case scenario," IF the cats are a problem, would I lose anything going to just a single aftermarket cat, maybe 3" or so? Or should I go ahead and replace both cats? I have the stock manifolds and would likely put headers on at the same time.

AFAIK, the cats are original, 176K+ on the car although the engine only has 80K or so.

Pat
'90 Formula (LB9)

 

Just get a single 3 inch high flow cat and you won't loose anything.