The sensor for 5s and 6s (not sure about the rest) is fitted to a small exhaust section
just off the turbo. You will not need to alter any sensor when fitting an aftermarket
exhaust or just the decat. The full Magnex exhaust (turbo downpipe, decat, system)
can be fitted without any worry about the sensor Just plug and play
Would recommend the Magnex for price/performance and fit.
Moby is talking about the High Temperature Sensor fitted to the E4 original CAT, unfortunately it looks like from Spanbody onwards they are talking about the lambda sensor which is entirely different.
Moby the High Temperature Sensor can just be secured out of the way (tape or cable tie out of the way). You do not need to fit it to an aftermarket exhaust system especially if you have a de-CAT. As far as I know it is purely there to detect whether the CAT is overheating and will display a warning light on the dash, it has no other use. The sensor was removed from the E5 onwards.