How I fixed P0171 (TOO LEAN)

I believe I managed to fix my several year running--SES light, old faithful: P0171.

Basically, my car did not like my Nismo CAI Gen II. It would throw a lean code, ping, spark knock, and get poor mpg while cruising. I tried replacing my o2 sensor and my MAF, like most people suggested. That didn't work. However, whenever I switched back to stock intake, my problem would go away.

So, I dug a little deeper and read about a strong positive correlation between larger MAF housing size and erratic MAF readings. Nismo is one of the few intakes that comes with an integrated MAF 3" housing.

I decided to order a honeycomb screen, which in theory would smooth out and straighten airflow before the MAF. This would allow it to read more accurately.

Jason, the owner of the site, suggested 1/8 cell--6:1 ratio. The cells were more dense as compared to the one used in the above thread by Westner, which should further help my issue.

I placed the screen right in the middle of the center coupler, a few inches before the MAF.

I reset the my fuel trims and ecu.

Normally, I would have a pending SES light in about 25 miles, especially if I cruised on the freeway. I pulled over about 30 miles in, and checked for pending codes. Nothing. Well, I drove another 40 miles, just to be certain. Again, I found nothing.

I also noticed that:

1) My idle was really smooth. It was steady, unlike before where I would see it dip a few times.

2) MPG was higher when cruising. This makes sense as the ECU no longer needs to dump as much fuel to try to correct the lean issue.

3) Absolutely no loss in power, if anything it felt a tad faster.

So far its been several hundred miles and my old pal P0171 hasn't returned. And I realize my issue isn't common, but hopefully this thread helps someone out.