My CEL came on after I reset my air fuel mixture. I put a new header on the week prior. It was fine for the week after I put the header on, it only came on the day after I reset the air fuel mix. The code read p0133 (o2 sensor slow response bank 1 sensor 1) I replaced the sensor. It still came on. The voltage off the sensor is about .15v at idle. Is this too lean? How to I get it higher.

I bet the header (removes the primary cat) is fouling the O2 sensor. Google O2 anti-foul and see if any of those DIY solutions fixes your problem.