Trying to keep my car close to stock ish. Has anyone ever removed the cat from the stock downpipe. Or would getting the OEM JDM downpipe be better than a USDM OEM decat DP?
Thanks

 

I believe most of us just get a good aftermarket downpipe - a nice smooth tube for best performance. Hardly anyone looking under the hood can tell the difference.
Getting it ceramic coated can help a little more with underhood temperatures.

 

^This.
It's a bolt-on item, so you can always save the OEM pre-cat if it helps you to sleep better. But the pre-cat definitely needs to come off. And using the jdm version wouldn't be any more "original" to your NADM car than a quality and better performing aftermarket DP.
When choosing one look for good welds, thick flanges and the mounting ear on the downstream side for the bracket to the side of the transmission. Not all of them have that.
I second having it heat-coated or at minimum, header wrapped with the spray-on sealant. I suggest chasing the mounting threads on the header before reinstall and using plenty of hi-temp anti-seize too. Plan on buying a new OEM gasket. They're a little pricey, but it's not a job anyone wants to do a second time.