As of lately my 350z has been throwing a P0128 Thermostat Function code. Now my question is, could this be triggered by a low temperature thermostat, or is the thermostat garbage? The code appeared before I installed my Koyo radiator.

This is irrelevant to my cooling system code, but I also noticed that my car occasionally sputters at around 3000 RPM and 3500 RPM[not every time I drive it]. I have been getting multiple rear o2 sensor codes [bank 1 and 2]. I cleared the o2 sensor codes without remembering them. I recall,
P0158 Rear O2S, Bank 2
and
P0138 Rear O2S, Bank 1 Maximum Voltage Monitoring.

Would these rear o2 sensors cause driveability issues?

I did throw a Random misfire P0300 after I replaced my radiator, but i'm assuming it is because I had to remove the MAF sensors on the intakes to get to the radiator. the code never returned. Any suggestions? Would love to hear your thoughts!