p242d gas exhaust temp sensor

Question

i had a tuner and exhaust installed and my truck has been acting up lots of blueish smoke comes outta the tail pipes and a (stop slowly now) appears on the dash of my truck as i lose engine power for a few seconds. This only happens if i keep the tuner settings on anything but the straight STOCK> p242d code appears when i look at the diognostic function on the screen of the tuner and i try to delete it and it pops back up again in a second