New (to me) Cats and Mid-pipes for my LQ9

[#1taho]

It's on my to do list. But I still hope not to run 91. We will see what happens. I will check the owners manual

 

[jough]

UPDATE #1: Initial problems....1. Must use the 5.3 oxygen sensors with the 6.0 cats. The electrical connectors are different. Donor was a 2004 Yukon Denali.
2. Get a passenger side exhaust manifold from a 6.0. 5.3 PS manifolds have a cone. 6.0s are the same on each side, like 5.3 DS manifold. Also added Magnaflow 15734 cat-back.

Engine immediately began missing and PS cat overheating. CEL came on. Lean Bank 2 and Random Misfire. PS front O2 sensor was covered in black soot after less that 10 miles. Put in new front O2 sensors on each side.

Shop disconnected the MAF and it still ran. They also disconnected the electronic throttle and idle went up. We initially thought there was a vacuum leak. Eventually it began running on all 8 with no CEL. I am so glad I took it to a great muffler shop for the install. The guys are familiar with LS engines.

My guess is that the free flowing cats and cat-back put the engine mapping into an unfamiliar area. My hope is that the ECM will continue to learn and optimize to the new exhaust. I have 2 long highway trips this week. That should help it all settle in. Even now hitting on all 8, power is down at the moment versus previous set-up, but I only have about 35 miles on it.

Exhaust note is now more aggressive, even at part-throttle. Did not notice drone. Did notice louder freeway cruising sound. The 3.5" tailpipe is likely a contributor.

Hope to have power & gas mileage update this weekend.

 

[#1taho]

I am not able to use my passengerside manifold, it has the egr tube into it. good catch on the o2 sensors.
do you think your tune will adjust to your exhaust?

 

[jough]

I think it will. Time will tell.

Exhaust shop switched PS flanges on cats.

 

[#1taho]

I was going over my truck and the 6.0 the other day, I don't know what intake would be better to use. The 6.0intake looks taller than the 5.3 , I have been told they re the same but look different. my thoughts were to use the 6.0 intake and throttle body and change out the fuel system, what did you end up doing?

 

[jough]

5.3 flex fuel intake assembly. Mine has return line.

 

[jough]

After about 1,000 miles, I am loving my new set-up with the 6.0 mid-pipes and Escalade Magnaflow cat-back.
Low end is now stronger. Mid and upper end is significantly stronger. The Magnaflow is a touch louder than I would prefer, but NO drone. I guess that I picked up at least 25hp. Again, it is significantly stronger now. I think that it will pay for itself in about a year, but I'm still collecting mpg data...so far about +1.0-1.5 mpg. I would do this again. Second gear is absolutely awesome.

 

[mattluttrell]

I'll be curious to hear how this goes. I have a tuned 6.2 Escalade and am curious about exhaust.

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