I don't see the CAI affecting coolant warmup time, open/partially open thermostat is a different matter.
Running cold coolant for a long time may be pissing off the ECU. Maybe try cardboard in front of part of the radiator? This will limit cooling, speeding up temp rise. Try 1/2 or more of the front surface.
What are your LTFT's? Depending on where you look, P1166 can be AFR's, pushing limits of trims or O2 heater circuit.
Most places lean towards replacing the sensor, but yours is about a year old.
Does your CAI go all the way to the TB? If not, do you still have the stock accordion elbow?
Thanks for the thoughts Charlie. While reading your reply I remembered why the thought of my CAI effecting it came to mind - some time about a year ago there was a period of time when I lived near a highway onramp that I accessed daily, so my car would be about half warmed up when I reached it. Sometimes I would give it a few "spirited shifts" to get up to highway speed and I could literally watch my engine temp gauge go from half warm to literally drop back down the the "cold" pin as I was romping my way onto the highway. Then it would raise quickly to where it was as I continued driving normally. That happened a few separate times. So it got me thinking that maybe the increased air through my intake was cooling my engine to some extreme. Now it seems more likely that my thermostat was probably falling on it's face.
Not sure on the LTFTs, I'm only using a very basic scanner to get my CEL code. I'll try your tests and go from there, if I change the thermostat and coolant temp sensor with no results I'll point toward that primary O2...
PS, my intake is all aluminum piping, it does not have the accordion-like piece.
Do your brakes work fine all the time? Reason I ask is it could be a crack or split in the brake booster line or even a failed check valve or leaky booster itself.
Yes they do... it worries me that you ask! Lol. I just finished up a pretty in-depth brake job actually, rotors and pads front and rear, both rear brake lines, and fresh brake fluid of course. The CEL existed before the brake job, but I will take a look over the brake booster and surrounding brake system, can't hurt to check. Thanks for the idea.
OEM? Aftermarket? Used/new?
It's an OEM "Siemens". Bought from Auto 7 through Rockauto, came in a blue Hyundai box and looks 100% identical to my OEM that came off. Unfortunately it's $110 that I didn't need to spend