Had a similar issue and mechanic found that I had multiple vacuum leaks (exhaust manifold and other areas)- this also was the cause of the DSC not available, etc.
Hope this helps

 

Exhaust manifold leaks are NOT vacuum leaks. They only cause noise because at that point the exhaust is under pressure and not vacuum. So you will gets noise which usally goes away or at least gets quiet when the engine warms up and the exhaust manifold expands with the heat. You possibly could get an O2 senor code if the crack is large enough to let in air but I think that would be a stretch.

The V6 is well known for vacuum elbow problems but not the STR.
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Those types of problems should not give a DSC error. You should have got the standard P0171, P0172 type stuff?
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The confirmed issue was the Bank 2 cat. They were covered under warranty until 70k miles. BUT, I deeded to go with Magnaflow high flow cats instead.

I went with part # 59975 as most of you have here on the forums. I just picked her up from the exhaust shop that did the work and am very happy to say that she is running better then every before. I am planning to finish the exhaust with a Magnaflow x pipe (resonator will be removed) and new mufflers (dont know which ones yet).

I believe a THANK YOU is in order for everyone that responded to this thread. It is great to be part of a community that can come together and help one another.

 

Well you deserve a thank you too because we need to have people report back with the final fix or we are all shooting in the dark. We are now seeing more and more cat failures on the STR.

This is a change.

One other thing? How much was the cat?
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I purchased them on Amazon, link below:

http://www.amazon.com/Magnaflow-5997.../dp/B000XQM3O2

I am sure that you can find them cheaper if you look around. I was in a rush to get them on the car so I went with Amazon.

 

Go with Borlas's

 

Thanks for that. Just don't use them in California because they are not approved.
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Do you have the part number for the ones that you went with, or a link?

 

I have the part number and will get it to you in a bit. Chrisstr gives it in his "Borlaflow" thread.

 

Happened to me with my 05 S Type. Dealer replaced the throttle body. Fortunately it was under warranty. No more problems after.

 

awesome it's fixed.

 

05BLKSTR. the Borla's were purchased from Summitt Racing, part # BOR-40358 $99.95/each. These are 2.5" inlet/outlet. Summitt carries 2.25" Borla's too. Today, recieved the replacement Magnaflow hi-flow cat to replace the bank #2 failed Magnaflow hi-flow cat (CEL w/restricted performance.

 

Glad we could help. Also glad that you posted up a fix, thanks...

Like "T-Bird" stated. Too many times we help only to have the user fly the proverbial coup! Not truly knowing if their problem was fixed... Got to think it was since they left....

 

Thank you for the information.