You can still pass without the muffler in CA, as long as it has the cat. My dad has a straight piped '06 CTD with the cat still in place, and his passed last month. No issues. Although, depending what city youre in, the "noise police" kinda frown on excessively loud vehicles.....CHP especially.
When I first straight piped my truck, cat in place, I pulled my 28ft travel trailer to the mountains for a weekend camping trip. I was going up the "El Cajon" pass and my truck was WAY LOUD pulling that load up-hill. Too loud even for me. Well, I got pulled over by CHP due to loud exhaust. I wasnt surprised. I was a POPO at the time so he let me go with a finger shake. MBRP later took care of that issue. But when I moved to Texas, my cat "somehow" went missing.

 

Muffler is not an emission related component

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id say, gut the cat and put it back on

 

Yep. I did that for a friend of mine. We pulled the cat, gutted it, and slid a 4" piece of straight pipe through it, letting it stick out about an inch on each side. I welded that together, and welded the damn thing back up. Looked totally stock and worked great!

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The smog cops just wanna see that its there is all......

 

Exactly, whether it works or not is a different story