Dual exhaust on 6.0 litre HD

I have a 2002 k1500 hd Sierra that has been dualed out with 2 flowmasters. Originally, it had dual pipes running into a single muffler with single out. I have been told that making it a "true dual" will throw the oxygen sensors out of sync, and flowmaster recommends replacing the mufflers with a new one they just came out with: #530504 "big block muffler for 6.0 & 8.4 L hd trucks" . Has anyone else heard this, or are they trying to sell me another muffler?

if the o2 sensors are in front of the muffler, they won't notice the difference.

they're trying to sell you a muffler.

keep in mind that decreased pressure in the exhaust will equal better flow, but the computer will see that as well. but you won't mess with o2s.

in my 99 6.0 i hve true duals and have no problems