Have you contacted PPE to see if they have other customers that had the same issues because it seems like there's at least two people in this thread that had the cel light up after installing ppe headers. Maybe they can point you into the right direction. I was thinking about get a set of ppe headers but will wait till you have your issue resolved so that I don't encounter the same cels.

 

Update. Picked up a generic OBDII scanner with Torque Lite to try and monitor some values. While monitoring at idle at operating temp the light went off. These are some of the stable values at warm idle, let me know if anything appears off.
MAF 4.5 g/s
Short term fuel trim 0-3%
Baro pressure 14.4 psi
Timing advance 13
Vacuum 20 inHG
Load 26%

The 26% load at idle seems high to me. When I first started the car from cold the short term fuel trim was at about -8%.

Note the only thing I have done is remove the intake pipe and reinstall. Possibly may have fixed an unseen air leak. Next step will be to drive around and see if the fuel trims stay good. Unfortunately this app does not show long term fuel trims, and for some reason the upstream O2 sensors voltage will not read (worked on my S10). Downstream is a steady 0.8 volts.

 

Short term fuel trim really means nothing by itself. It will change rapidly. The load is not outside of range at idle. You need to look at the combination of short and long fuel trims. Add the two together and they should be within +/- 10% as that is the range the ECU is shooting for. Outside of that you could find that you throw P1170.

 

Also, know that these codes are most common with a false air reading (vacuum leak). It would be worth your time to go through all of your connections are verify there is no leak.

 

Check Engine Light With Code P0171 and/or P0174 on Lexus ES330. The Check Engine Light may illuminate with codes P0171 and/or P0174 due to a lean running engine. Symptoms may include: Hesitation on acceleration, lack of power, and poor fuel mileage. This is commonly caused by a dirty mass airflow sensor.

https://www.autocodes.com/p0171_lexus.html

Hope this helps and good luck

 

I have a is350 with a cold air intake and I have both babks running lean and the port injector code with terrible gas mileage

 

You'd have better luck posting your issue in a new thread with freeze frame data from your code reader. This thread is nearly 3 years old.