I've ordered my dpf/cat delete and have a question where the flange comes off of the downpipe how are you guys getting the bolts out because they look like they are tack welded.
How much are the sensors?13mm IS the flare nut size for the sensors, use very good quality wrench. As far as the bolts for the DP flange, you can only un thread the bolts from the front. I use a 13mm 6pt shallow flex socket on a 12" extension and ratchet, it gets right in there. Use plenty of lube on the sensors before trying to remove them, let it soak in first. Usually the rear one is the only stuck one, if it fights me I just replace it.