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i am having a hard time whether to go with a high-flow cat, remove the cat and get a custom straight/downpipe, or just leave it as is...i have the dc sport headers and it is only the 4-1 for our car so i was wonderin if it really would make a difference to either remove the cat or add a high flo cat....people have told me that it doesnt make much diff, some people say it makes a big diff, and some say it ****s with ur ecu(air/fuel management) and ill be screwed in the long run cuz of a smog test...what should i do? please help!!

 
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it only messes up the ecu if you don't put the o2 sensor back in the pipe...you'll need a simulator to cut off the CEL, though...WannaBFast has them for 20 bucks plus shipping

 
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i have the dc header and a "hi flow cat". which is basically a pipe with a resonator on it.

i had trouble with my car running lean at WOT and rich at idle.
to solve this i plugged the o2 sensor before the cat in and attatched the o2 simulator to where the second o2 sensor is supposed to plug in. it ended up working great. now the car's fuel pattern is about the same as stock. it sometimes runs a wee bit rich but id rather it run rich then lean

 
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I'd go catless. On our cars, it's just been proven to show gains providing you know what to do about the O2 sensors.

 
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so if i kno what to do with the o2 sensors then going catless is the best way? but how much will i really get outta it?

 
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Run a straight pipe. You'll feel a gain but it's not going to be back to the future.

 
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what kind of gain 2-5 hp?

 
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You can't feel a 2-5 HP gain. With a header you could be seeing more like a 10+ gain. It takes around that much HP to feel it in the entire powerband.

 
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Dont get Dc header it sucks

 
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which header should i get then?

 
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Im fine with my ebay header....

Somone please pm me about the 02 sensor stuff!

Ive been running with the CEL on for a while!

 
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Are you running a high flow cat or no cat? Because if you are, and the car throws a CEL, there's nothing you can do about it. Pretty much if you were to take your car to a dealer and have them put your car on that magical machine that tells all of your car's problems, it's going to say the light is on because you're running a faulty catalytic converter. There is no fix for it.

You can get the O2 simulator (or an MIL Eliminator) to turn the light off but it only tricks the ECU into thinking you're running the stock cat

 
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kamikazi for dx/lx HP for others and yea run straight pipe to resonator to muffler (please.... stop the rice, run a resonator = ) )

yea its def at least a 10 hp gain, i put on aem cai, kami headers port matched exhaust ports, and the revo short shifter all at once and it was like driving a new car i would swear it knocked a sec off quarter but you know how that goes.

ps yea you need the o2 sim

 
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^^ agreed. I don't have a reso right now and it's ****ing LOUD! LOL. Get a reso.

 
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Ok not thread hijacking but want to ask a question. I have a 2k2 lx and want to install a whole new exhaust and would like to know should I bother buying the ex setup or should I buy the lx top portion header and hook it up to a megan downpipe and highflow. Since I have heard if I do the ex conversion I have to buy the ex sway bar as well. Sorry if it is a noob question.