I ordered the Cornerstone Performance catless midpipes but I will be running them without a tune. The only other modifications done to the vehicle is a Borla cat back and a AFE CAI. Will the ECU be able to adjust to the new AFR or would this be unsafe to run without a tune?
Catless midpipes and no tune
- Thread starter Hairston
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If an O2 sensor is plugged into those cats, as i suspect, then you will get a CEL. The car will run rich to protect itself. you will likely notice some performance increase but nothing near what you would if you hacked the ecu and tune it for no cats. I could be wrong so hopefully other members chime in. I would love a sound clip btw.
Yeah I am getting some O2 simulators to avoid the CEL. As soon as I install them I’ll send a sound clip.
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Yes, please post up a sound clip once installed and initial impressions. I am thinking about going the Cornerstone route or with the GT Haus catted mid pipes.
I run the j style O2 simulators to avoid the CEL with my cat delete. You will not notice any power increase running catless at those levels. I didn’t notice any power increase running 18 psi out of the blower at about 1000chp going catless. Only did it to avoid hurting the OEM cats in case I ever want to sell with them. You will notice the power band move up in RPM, especially without a tune, which will actually feel like the truck got slower as it loses a bit of low end torque. Personally running catless with the current exhaust system sounded too raspy so end up adding some vibrant resonators.
I had JBA ones on my Scat , all the rest of the exhaust was factory, it sounded great , deep , loud. It sounded like it had an aftermarket exhaust, and headers.
Do you get a noticeable fuel smell from the exhaust (with or without a tune)? Do the O2 simulators trick the engine to run leaner to limit the fuel smell? I imagine with a tune you can make the engine run leaner thus reducing/eliminating the fuel smell but without a tune is the fuel smell obnoxious?
Debating between Kooks LT catless and green cats. Would prefer to save over a grand by going catless but not looking forward to a heavy fuel smell from the exhaust (ignoring a proper tune that would void the warranty). Thinking green cats is the way to go but hoping someone with catless experience can provide insight into all the pros and cons. Anyone else running headers (catless or catted), feel free to weigh in.
When you are tired of the fuel smell, the drone, and the exhaust sounding like a 1989 straight piped Camaro, we have the Gt Haus high flow cats in stock 
I run e85 99% of the time so the fuel smell doesn’t bother me. Don’t notice it in the truck at all. Rear O2s aren’t used to change fuel trims and I wouldn’t recommend trying to tune for a lean mix in any conditions (including idle).
I would just go the high flow cat route especially if you are going to run pump gas.
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