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P171 code on 2006 toyota corolla

I get this code, p171, every so often on my corolla. I have cleaned the MAF and finally changed it with one bought at AutoZone. I still get the code. What should I do next?

Does this only occur when the temperature is below 50*? And usually within a few miles of a cold start up?

You know, I have not kept track. It might happen then. It did not happen before this year. Do you think it is the intake manifold gasket?

Why did you change the MAF? Cleaning it would be a first step. Replacing it might be about step 20.

Step 2 is to check for vacuum leaks. One place you can get one is via the intake manifold gasket, but there’s no reason to assume that right off.

This code is also sometimes set by an O2 sensor problem - since its the O@ sensor doing the reporting.

This is a pretty good write up of the code:

Thanks for the link! I will check for vacuum leaks and look at the O2 sensor. You are right, the MAF does not appear to be the problem.