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Hey guys, looking for headers for my 330xi and everywhere i search up on this is arguing normal 330i headers fit or don't so whats the real answer? are they xi specific or not? also any suggestions on headers ? i have read about ebay headers and there horrible fitment so im guessing i should stay away from those..
 

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Do the Canadian versions of the 330xi have the CATs double as the Exhaust Manifolds? If so, when replacing them with Headers, what is the plan for the O2 Sensors and CAT(s)? The Headers will increase performance by having the exhaust "tuned" for better flow, but at what cost? Here in the States, especially States like Pennsylvania, you have to pass emissions tests once a year at Inspection Time, if Headers are put on, the O2 sensors need to be put some where else and a CAT or 2 need to be installed in the system (unless the car will be used on the track and not as a street car). Definitely going to be a tight fit with all that's going on in the engine bay and sure looks like a complete custom exhaust system will have to be made. Should sound real sweet though. If you go thru with it, you should take photos and do a write up for here so others can see what you went thru including the final cost.
 

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You can do a sim and still pass emissions, just have to talk to the right people. Im probably going to end up doing race cats built into my exhaust when I redo it. But that wont be for awhile, got too much other stuff going out before then. Until you have your inspection your car runs fine, just has a check engine light. Oh, and tight fit is an understatement, just sayin.
 

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Here in PA, if a check engine light is on during State Inspection and State Emissions Inspection, it fails! And anything newer than Mid 90s MUST have emissions system complete and working, they hook up to computer and check for codes. Mid 90's and earlier are exempt except for gas cap testing. So, CAT(s) and O2 Sensor(s) would have to be worked into system to pass the Emissions Inspection, not too many Inspection Stations will turn their heads and look the other way cause they can not afford to loose their Inspection Station Licenses.
 

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There's plenty-o-information on XI fitment of headers but you have to dig. There's two schools of approach. One, intent on keeping pre/post O2 sensors where only certain headers allow clearance of the sensor with the bung (threaded insert) position. Many spent hours installing only to discover there was no way to install the sensor. Second option is to abandon the O2 and cat/cats. They use an emulator to "trick" the ECU that it has a sensor or hello Check Engine lamp. There is one company that offers headers with small cartridge cats that fit properly. I recall the setup was over a thousand dollars!

It seems for the effort required to install them, adding after-market cats ($$) with R&D required to fit O2 sensors, it's questionable if it's worthy for the minimum gains. Many don't realize the more free flow exhaust you create, the more you take away from low-end torque. The gain is seen at high RPM where low/mid actually loses HP. Sure, you can make a louder exhaust tone but actually decrease off-the-line performance. If you want sound, change out the muffler. Don't cut up a well designed and efficient system 'cause you're more clever then factory engineers. If you really think dualed cats, pipes and resonators weren't tuned by the factory for proper back-pressure and cylinder scavenging please chop her up and enjoy a nice driver... that sounds like a Fire Truck.
 
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