my fathers 08 specv was recently gifted with a new M2 racing header it works fine excpet its throwing the SES light and after driving for atleast 30 minutes it starts to sputter when driving at a constant speed such as highway driving. Also it is sucking gas like a MF. I tried the anti-fouler to back out the o2 sensors but made it worst...keep in mind i dont want to have to spend a lot of money to solve the problem... Help Please!

I assume the codes are for the O2 sensors?

Make sure they're installed in the right order. You may have to move the rear sensor back behind the cat to clear the code.

which of the 4 sensors did you space?

You may need to make your lower o2 sensors the prior type from the 07 specv. Different part number, same connection. Some odd reason mid 2007, nissan changed the lower o2 to a different design. the prior gets no codes, and the newer ones do.

I have an 08 spec-v as well with a megan header in it. My SES light comes on sometimes as well but I have only spaced out the o2 sensor in bank 2(which is the one on the right side). I have been able to drive for roughly 1000 miles before the light came on before. It comes and goes to tell you the truth. I am going to try and space out the other o2 sensor to see what happens. In my spec-v, the upper two sensors are actually air fuel sensors while the bottom two are heated oxygen sensors. Not sure what djtorello is talking about tho. Also before I spaced out any o2 sensors I was just getting code p0430, which is the code saying catalyst efficiency below threshold, bank 2. So I spaced out just that one sensor. Now when the SES light comes on I get codes P0430, AND P0420, which is both bank 1 and bank 2 sensors. I will try to space out the other sensor to see what happens. Might have to try an o2 simulator eventually.

Speaking of the devil, damn SES light went off after I left work last night. Just turned the car on and bam, gone. Drove around this time for about 200 miles before it turned off. Seems to be random....still have not spaced out the other o2 sensor either.

The lower two sensors should have spacers. That method is hit and miss in general, though.

Essentially, the first two send a signal to the ECU to indicate AFR. They really only ensure that the AFR is not wildly out of spec. They're not particularly sensitive.

The second two are to ensure that the precat is working, hence why in the stock manifold they're after the precat. They're purely an emissions feature.

bank 2 means lower sensors, not just 1 side.

you have bank 1 sensor 2 and bank 2 sensor 2, both indicate lower sensors.

Bank 1 is the left, Bank 2 is the right. Sensor 1 are the widdebands, Sensor 2's are emissions.