I have a 2014 scion tc with aftermarket headers but no tune. The car is running so lean that sometimes it stalls out a red lights I was wonder how I was disable or bypass the o2 sensors.

 

A header shouldn't cause it to stall out, mine never did before I was tuned (nor did it pop a CEL) and I've never heard of a header causing that on anyone else's cars on any platform. I'd recheck your header install and that everything is connected and check for vacuum leaks and confirm your PCV is functioning properly.

If you're sure it's the header, then get the car tuned - it's an available platform in VF Tuner now. You can't disable the O2's anymore legally due to some new legislation, but a tune should help get your values in the right place. If tuning is out of the question for some reason, I'd test your luck with one of those Vibrant O2 sensor spacers.