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I have a 2008 ford 4.6L mustang I bought recently. I got it off auction so I don't know anything about the vehicles mod history.

From what I can tell, the owner put on Borla exhausts, cams, and a tune. The owner left his original SCT XCalibrator 2 tune installer with 2 tunes and 1 stock tune on it.

I need to pass I/M readiness, but my Cat, O2, and O2 heater sensors are incomplete. Ive tried all the drive cycles I can find, and have put on over 150 miles trying to get them to complete.

I wonder if the tune has the rear O2 sensors turned off to keep the MIL from turning on. I'm also wondering if the high flow muffler delete Borla exhaust’s will affect the completion of the sensors.

Ive read in other forums that people go back to stock exhausts and stock tune and have the issue fixed that way. But I don't have the luxury of having the stock exhausts with me. Ive read about other people putting plates in their exhausts to restrict airflow and allow the CAT to heat up to the correct activation temp.

If you guys have any solutions or any ideas, let me know! Ive been trying to fix this issue for the past month, and I need to pass inspection asap in 2 weeks. Any help is greatly appreciated 🙏
 

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I don’t have the answer for you, but hopefully someone will chime in to help.
 

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Tech Advisor
2006 Mustang GT Deluxe
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The muffler deletes shouldn't affect the O2 sensors since they're much further downstream but if your mid-pipe is catless, it's likely the rear O2 sensors have been disabled in the tune. In that case, the best solution is to have a pair of high-flow cats spliced into the front half of the mid-pipe and have the tune revised with the rear O2 sensors enabled. You didn't mention whether the car has headers so I'll assume it still has the stock exhaust manifolds.
You did mention that your SCT X2 tuner has two tunes in addition to the stock tune. If you can identify who provided those tunes, I suggest you reach out to that company or person for a revision.
Do you know which cams were added? The most popular are the Ford Performance Hot Rods and the Brenspeed Detroit Rockers, so it's possible whoever supplied the cams also supplied the tune to go with them.
 

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I had same issue on 2011 GT. Have Roush supercharger with Roush axlebacks. Couldn’t get O2 sensors to ready state even though I was able to do that multiple times in the past. Super frustrating. Fought it for a couple years and just got it solved. First I confirmed with tuner that O2 sensors were not turned off. Assumed that was the case due to past success but double checked anyway. They recommended against going back to a fully stock tune. Then I had a mechanic confirm the O2 sensors were working as expected. They concluded there was not enough heat building up at the sensors and suggested putting stock mufflers on assuming those would cause more heat to build up compared to the Roush mufflers. I found stock mufflers on Facebook marketplace and had them installed. After drive cycles particularly running at 70 mph for 5 minutes several times in a row, the O2 sensors came ready. I passed emissions test and swapped the Roush exhausts back on. I would definitely try this route before doing more extreme exhaust modification. Hope this helps.
 
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