Thanks to all who have contributed. This post is truly, the most helpful comprehensive resource available for downpipe installs on our platform.
After having completed the install myself I’d like to further add to this thread, to help others noobies like myself who who would like to DIY the install.
My install - I installed MAD Catless DPs on my 2021 G82 11k miles, using a lowprofile Jack and flat topped Jack stands. I did the install alone; Install took several days. My mechanical knowledge is novice to intermediate.
Helpful tips:- Label everything, especially fasteners (nuts, bolts, etc.) there are a lot that you will remove and you will forget where they go.
- Use a fastener lube (rust pen, WD-40, etc.) on all the exhaust bolts above the mid pipes including: connecting pipe, downpipes, and O2 sensors (obviously don’t get anything on the sensors themselves).
- As another contributor mentioned about using a flathead screw driver to remove the part connecting the downpipe to the Turbo Assembly….. to clarify, this is the V-Clamp - the gold colored clamp. You must completely remove each clamp to break the downpipe free. An extra long flathead or prybar will help and you may have to use a rubber mallet on the butt of said flathead/prybar. Note that even when you completely remove the bolt, the clamp remains attached very tightly to the downpipe until you pry it off, thus freeing the downpipe.
- As this same aforementioned contributor mentioned, don’t forget to pull off the metallic colored, rubber flanges off of the OEM downpipes from the side that connects them to the mid pipe, as you will reuse these on your new DPs to connect them back to the mid pipe/connecting pipe.
- When you are in the engine bay, it is helpful to disconnect the two connections running to the positive battery relay, in order to access the O2 sensor that is right there and to also fish the connections back and forth. As was mentioned in this thread make sure you disconnect your battery, which is located in the trunk under the flat carpeted liner, before you even start the install.
- If installing mini cats (big daddy’s garage spacers), they go in the O2 sensors closest to the rear of the car in the long and short DP, respectively.