i have 2010 lexus is250c and have an intermittent engine light p0420 only 99% likely failing catalytic converter (exhaust manifold) on the passenger side.
I have done my research and it is for sure that 17140-31510 is the exact number for the 2010 model.

https://www.lexuspartsnow.com/parts/...140-31510.html
https://www.lexuspartsnow.com/parts/...140-31640.html
https://parts.lexus.com/p/Lexus__IS-...714031510.html
https://parts.keyeslexus.com/oem-par...old-1714031510

However, 17140-31510 is about a couple of hundred dollars more expensive, and wonder if 17140-31640 would be fit perfectly.
some says 17140-31510 fit both 2010 - 2011 sedan and convertible, and 17140-31640 covers from 2010 base or 2011 all through 2013.
It just does not much sense how this 17140-31640 would not fit into the 2010 is250c model.
Does anyone know if they would share the same exhaust manifold?

Thanks

 

I ended up purchasing a salvage 2008 lexus IS250 exhaust manifold and it was 100% compatible.
Monitored voltage of Bank 1 Sensor 2 and it is just as good as Bank 2 Sensor 2.
Hope this part last long (per seller, only had 28k miles on the cat. converter).
Hope this information is useful for those who have failing cat converter.

Note that, the exhaust manifold for these vehicles are easily $1000 +, or even close to 1500 at dealer.
Only mechanics can install these parts and it will cost $$ for the labor itself. Do your own research and would be better idea to avoid aftermarket part while searching for good salvaged OEM parts unless you want to go w/ new OEM parts.
I got my cat. converter for less than $220 w/ 28k miles fyi.