After my tune this code popped up: (W211 E63)

0908- G3/4 (Right O2 sensor before TWC [KAT]): Signal implausible (P0130)

Car idles rough at times and surges rpm, mpg is down and I'm assuming I'm being robbed of some power ever since this code was thrown.

Cars is Longtubed and catless.

So change the O2 or could a connector be loose or could this be something with the tune? This light came on literally with in 5 miles of the car being tuned.

Thanks