How much do headers affect the air/fuel ratio?
I have some what the same issue. I can almost afford to do headers and what not. I just cant afford the tune.
fellas you really should have accounted for the fact that its a good idea to get the tune with the headers, thats not smart planning but it is your car....
your going to be very upset with your cars performance if you cant get a proper tune
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I put MAC headers and cat y pipe on my car. No tune. I lost bottem end torque and only picked up a bit of HP on the top. I was dissapointed to say the least. Lots of work for no real gains.
We have a local dyno sniffer test in our area. I have the sniffer results before the header install. The levels were very very low. My car was clean. After the header install my car failed. All the levels measured shot way up. I could not find a local shop that could tune, so I swapped the old exhaust back in. The headers I took off were covered in a thick layer of black soot. The car was very rich. After the car passed with the stock exhaust and with the same very low levels.
What did I learn:
1) don't bother with mids, get LTs
2) get a tune, even if you have to buy HP Tuners/EFI Live
3) Get quality cats like Mangnaflow - OE generic cats are **** - they are efficent enough not to set off SES codes, but not effective enough to pass sniffer tests.
Before I took the headers off, I had a shop drill holes in the Y pipe before and after the cat and measure the efficency. The new MAC cats were only about 50 to 60% efficient. They told me you need atleast 70% or even higher for an OBD II car.
I've already lined up a retune so I can get the most out of them, but yours should run fine in the meantime.



