Magnflow muffler advise please

Hi All!

Am planning on having a Magnaflow muffler (dual in / single out) hooked up to my 2010 Armada LE since I've found out that the Gibson exhaust system is a single in single out!

I've searched and been through 9 pages and it seems the Magnaflow mufflers are the best choice. They have a bit of drone between 70-80mph but I can live with that (my G35's HKS muffler had drone and I was fine with that for 6 years).

A few questions:

1. Which muffler is less noisy:
Muffler #12588 (http://www.magnaflow.com/02product/d...rtnumber=12588) - 22" muffler / dual 2.5 in / single 3 in out
Muffler #12580 http://www.magnaflow.com/02product/d...rtnumber=12580. - 22" muffler / dual 2.25 in / single 2.5 in out
Stock Armada is

2. Are the above mufflers bolt on or need welding? I looked at the service manual (see attached pic) and it seems that the two pipes connected to the main muffler are not removeable.

3. Is it advisable to get new gaskets?

4. Is it ok to use the stock tail pipe with the Magnaflow muffler?

5. What is the stock tubing size on the Armada - 2.25 or 2.5? I read that keep the aftermarket muffler to similar specs as the stock diameter is better in order to minimalize loss of low end power.

Thanks!
Clint

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