Questions regarding service warranty

[Yobao]

Hi guys,
So I took my car into the dealership today because a check engine light came on that says there is something wrong with the emission system. They did a diagnostic test that says coolant temperature sensor malfunction and that they will replace the sensor. It is also recommended that I pay $370 for fuel sensor cleaning and intake manifold cleaning. Correct me if I'm wrong (and I think I may wrong on this) but doesn't the service warranty cover these? And do you think that $370 is a good price for those two services or can a can of Techron take care of the job decently.
I've had issues in the past where the oxygen sensor went bad and it was replaced. Can I make the argument to the service advisor that that could be the reason for the rapid build up of soot in the engine? Or am I just being ridiculous by making that argument.
Thanks in advance for your help and opinions.

[Yobao]

My car has 25K on it right now, btw.