Need help re 2008 V6

[reiluvrockandroll]

Can someone please give me some advice. I purchased a 2008 V6 Commodore 3 weeks ago from a dealer. An hour after picking it up the engine warning light came on. I rang the dealer who arranged for someone to put iton the testing machine. It came up as fuel sensor which was changed. 4 days later on came the light again. Took it to my local dealer who put it on the machine and it came up stretched timing chain and he reset the computer. Drove it for a week no probs till on came the light again with warning lights and bells going off. Rang the dealer who arranged for it to be picked up.
During the good week I stupidly got the local exhaust centre to take out the resonator and replace the ends with that of an SS.
Today had to fly to Sydney to pick it up as was assured that he had been driving it all week and no probs. Got 20 kms away and on came the warning light again.
They put it back on the tester and they are now telling me that it is a different problem to previous and that it is caused by changing my exhaust.
They have been helpful but I'm at my wits end.
Could it be caused by changing the exhaust???

[rb26dett]

Sounds like the dealer is trying to get out of it. Did they tell you what the exhaust is supposed to have done to the car?

[reiluvrockandroll]

They are saying the oxygen sensor is giving a false reading