I want to start by saying I don't know a ton about about the inter workings of any car but I find it fascinating. I need to replace my left catalytic converter. My mechanic is fantastic and has kept my old guy running for some time. He called Land Rover parts and they want nearly $5k for the part. I replaced the right side for $1,400 two years ago. Do I have to buy this part from Land Rover? He think it will cause more problems if we don't use Land Rover parts. I bought my car brand new and I need to get another year at least out of it. I work from home so most of my travel is local. 2008 Range Rover Sport Super Changed 200K miles. Thank you for any help!