Why for some components is necessary to increase the length of the lambda sensor wires?
To fit Supersprint headers, turbo downpipes, metallic cats or cat replacement pipes on certain cars is necessary to move the Oxygen sensors downstream along the exhaust line (toward the rear of the car).
The Supersprint components are often designed with substantial differences from the stock components, to increase the exhaust system performance without any compromise.
Regarding the headers, the stock items are often too short, too twisted, or the cat is too close to the engine. To optimize the efficiency is necessary to use longer primary pipes with different routing, moving the cats and the lambda sensors consequently.
In case of downpipes, the stock cat is placed in the engine bay, very close to the turbocharger for emissions reasons from cold. We move the cat under the car so we can obtain both a turbo efficiency gain and lower temperatures on the turbo and in the engine bay, with better performance and durability.
To correctly fit the oxygen sensors on these components the wires must be extended.
Here's an example of an exhaust system that requires this kind of modification, in this case on 4 wires(Lotus Evora 3.5 V6):