2012 Nissan Frontier SV automatic V6 4.0 RWD 110k miles, south Texas.

I have two questions about my sweet little frontier…

I was getting a fault code and going to limp mode for a bad brake solenoid and others, so I replaced the valve body and TCM with OEM parts. I also did 2 fluid drains on the trans as it was dirty (OEM trans fluid).

Now it seems that when I’m accelerating from 40mph to about 65, the rpm goes up then drops and starts accelerating at a slower rate and the engine seems to struggle a little bit. No codes or faults, it just feels and looks like I lose power… any ideas? Idea might be to replace the fuel filter but it’s in the tank!

Also, she slightly shudders and drops RPM randomly on and off if I’m idle with the A/C on. I also notice that the A/C blows slightly harder and weaker intermittently and totally random while idle. I’ve read this is a common thing and just program the idle throttle/rpm higher to avoid it… any ideas what might actually be causing this? I’m sure they didn’t do it brand new!

Thanks for any help or advice!

-B