well im not sure if it is or not but if u read my sig it says with no tune. i installed my headers and didnt connect the rear O2 sensors because the headers didnt have them. ive had a check engine light ever since which i figured i would untill i could delete the rear 02's with a tuner. i guess my question is would u guys think ide b doing any harm or losing performance running it without the o2's deleted?

 

You are losing performance with the headers and no tune for sure.....its always best to have a tune for the LTs...but the CEL is from the rear O2s not being connected and it not hurting anything.