Exhaust size?

[Brians4x4]

I drive a 2005 tahoe. I recently got some 3 inch glasspacks, and I was wondering what size the pipes are after the catalytic converters. I know once the pipes come together they run 3 inches to the stock muffler. But i want to run true duals and cut out the y pipe and I want to know what size reducer I need to get, I think its either 2.5 or 2.75 inches. Thanks for any help.



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[1988 GMC 355]

2.75 is the size before the muffler

[oldred95]

The Y pipe portion of the exhaust is all done in 2 3/4 as well if I'm not mistaken. And its 2 3/4 from the Y back to the tailpipe.