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Some time ago I realized my car does not have a catalytic converter, however it still has the stock exhaust. I am the second owner of the car. Does this provide more power? What is the point of having no cat?

 
Rep Power: 812

the cat itself is fairly restrictive if you look inside, like honeycomb mesh everywhere. still, they flow well enough on high hp cars. but yeah alot of people ditch the cat for a race header that is just an open pipe. bad for the environment tho. they prolly didnt have money to replace it with if the exhaust is still stock around it.

 
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So do I still have to stick with LX/DX exhaust components or can I get EX?

 
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most likely yes, your still going to want to purchase lx exhaust parts.
UNLESS your stock exhaust is an ex conversion.But if both of your 02 sensors are still on the exhaust header, then it is not an ex conversion.

 
Rep Power: 812

if you switch to EX exhaust, you have to replace EVERYTHING if yours is an LX. you need EX header, downpipe, cat, and catback exhaust (with muffler). if you are saying they just replaced the cat/header on your car with aftermarket (because cat is part of the header manifold), then all you need to go back to stock is an LX oem manifold with cat. if you want to convert to EX exhaust, you need all the ex parts including new manifold.

 
Rep Power: 257

is your car throwing any codes like p0420 ??? if not you could just have a universal cat converter welded on to your existing exhaust.