so i just replaced the headers, opti, plugs, wires, water pump etc, i had a misfire from my bad wires so after i changed all that i still have a check engine light and my mpg dropped from 16 to 8 i guessing now it must be o2 sensors any input would help

 

You need to scan that SES light to get a feel of where to go next

 

Sounds like a major exhaust leak somewhere. If you have a scan tool, check the 02's should be jumping up and down in readings constantly, not setting at one value too long. If you have coated headers, the inital heating of the coating will burn off and can ruin your 02's also. So check this out.

hth
andy schuck