2011 Altima. I've had a P0101 code for a while now. I have replaced the MAF sensor with a Nissan Genuine Part, but have yet to have the dealer reprogram the ECM. The P0101 keeps coming up. Also at times the TCS light comes on and the car starts acting up when trying to accelerate at about 2400 RPM. This only happens at times and can last a couple days then just goes away. What can be causing this? Is it related to that P0101 code not being cleared from the ECM at the dealer?

See this bulletin:

https://static.nhtsa.gov/odi/tsbs/2016/ ... 2-9999.pdf

If your ECM part number suffix matches any of the ones listed, you need an ECM repro. There are numerous P0101 bulletins for numerous N/I models, and most are the result of the A/F sensor map in the ECM being "cut too close". As the A/F and MAF age electrically, the readings drift off the map. The ECM, not knowing its map is flawed, incorrectly blames the MAF. In general, the repros simply expand the A/F map.

Will this be the cause of the TCS light come on and the car acti g up at 2400 RPM?

Yes, the TCS light is probably the result of the ECM engine speed signal going offline when it throws the code.