B1 S1 Lambda sensor

[quattrocamper]

First of all...A BIG thanks to all who have answered my previous posts, sorry about the frequency, but trying to sort all the niggles. 1997 2.8 B5 avant Quattro:
Scanned with Vag Com, getting a persistent returning fault of B1 S1 sensor low or intermittant reading. Trying to troubleshoot if I need another sensor, or could this be something to do with a vacuum leak? Did think about swapping the sensors around, and seeing if the problem moves, but seems like a lot of hassle...Don't think these are going to come out too easily! Anyone had this? MOT due in a couple of months, want to get everything as right as it can be! Have also read that non oem sensors are not much cop...anyone had success with others?

[burkey1]

could be a leak but your suggestion of swapping probes is a good one.
Thats where I would start..

make sure manifold is hot when removing sensors and use copper grease when refitting