Cat Question
 

To make a long story short, two years ago I had high flow cats installed, and about 5 months ago they started throwing a code. I got O2 sims to take care of the code, but now I'm thinking of getting headers in a month or so, and I'd like to keep the cats that on there now because my budget is going to be stretched enough as it is. And yes, I need to keep the cats. So what I'm wondering is, if the cats are throwing a code does that mean their flow is reduced? There's no sulfur smell like they're clogged, just a bit stronger exhaust smell.

did you get the ceramic or metallic ones?

Ceramic

what code is the car throwing? do you notice the car losing acceleration?

I don't know the exact code, I took it to autozone to have the code checked. I think it was a low efficiency code, but I'm not positive. The guy checked the code, and I tried to look over his shoulder but he was too quick. Pulled the reader off and said "you need to replace your cats."
To me, the car feels like its a bit sluggish in 1st and 2nd gears lately, but it definitely could be my imagination. The car always feels slow to me, just cause I've gotten used to it.

cuz a clogged cat would make the car feel sluggish with a loss of acceleration-a low efficency code can be a bad o2. when i gutted my cats, my car was throwin cataslytic efficency below threshold

my car is throwing the low effenicy code have already replaced the O2's and took it the the dealership since i have the stock manifolds and cats the did there tests and they came to the conclusion that the passanger side cat is bad. the code that the car is throwing is PO430. hope this helps you out.

whens the last time you did a tune up? cats normaly dont just go bad. there is norm a reason for it.

Thanks for all the responses, I've already replaced the O2s with sims, I'm not worried about the code, I'm just wondering if the cats would be flowing badly as a side effect of low efficiency. That being said, I don't think they're clogged because I've had clogged cats before, and they had a very distinct sulfur smell. Could they be clogged up and not smelling like sulfur, because I had thought that clogged cats and rotten egg smell went hand in hand.
Omec, what do you mean by a tune up? When I first got the high flow cats installed, the car was running like crap (misfiring, idling badly, I'm never going back to that exhaust shop ever again), so I took it into a Chevy dealer and they did a tune up on it, but they said a tune up on a FI engine is basically just cleaning the injectors and the fuel rails. It fixed the misfiring and the bad idle, and I hadn't had any problems with the cats until the SES light came on a few months back, and fixed that with the sims. But since I'm getting headers in a month or so, I want to know if I should get the cats replaced at the same time because I don't want some badly flowing cats to be dragging performance down. If they're just not burning as clean, I can deal with that.

well is u are gettin long tubes and have the o2 sim then just dump the cat. dont spend the money if u dont have to.

I wish I could, but that's not an option. I at least need to have cats, even if they're not cleaning the exhaust like they should. What it comes down to is, is there any reason to think flow through them would be reduced just because they're low efficiency?

its reading low efficiency for some reason. id say first check out your plugs. fouled plugs will throw raw fuel at the cats heating them up. the cats may be getting more o2. if thats the case look at the up and down stream o2's. up steam o2's will be all over the place at idle (.01mv to .45ish) down stream should be a steady voltage. you shouldnt be able to see any change in the 02's after the cats. i thought i read some where you put in sims though. if thats the case find out what the sims are doing. cat effic is messured by the 02's after the cat.