Update, didn’t overheat the whole way to work. Once I pulled into the garage and put it in park and sat there for 2 minutes, then it overheated by 2 dashes on the gauge.
I have an SFR tune...Wow, If you are showing overheat on the bar gauge its waaay up there. There is no reason it should be anywhere near that under any circumstances.
I noticed you are pretty high mileage.
I also noticed you said you changed the thermostat after the 230 plus incident. Thats good because Im sure you melted all the units wax out, it wouldnt have worked right from then on anyway.
Try this as an experiment:
As your engine gets hot while idling turn the HEAT up to full, then put the car on vent flow like your were using the AC. Turn your interior fan up high. It should drop your temp like a bad habit. If it doesnt I'd say you have excessive aluminium corrosion in your entire system including the heater core. I know you have dumped your fluids recently but that would nt do the trick.
Use this according to directions. If you do it right you'll fill and flush at least three times.
Also of important note:
CSR and KOYO have stopped making the 3.8 radiator as of this summer.
I use Mishi's, I got it for free. I've had to warranty replace it twice, but they have replaced it no hassles every time. It does do a really good job of keeping her cool in any circumstance.(They develop pinholes). Then again it coud be my crazy motor and the way I drive.
If I were you I would do the above. I would also replace your auto zone coolant (hahah) with this when done with the flushing.
Global Antifreeze/Engine Coollant. Youll need to buy a full gallon of concentrate then add (drinking water),...NOT DISTILLED.
I have a boosted BK2 that runs pure meth, Im making near 600 at the crank, the above stuff works like a dream.
***For all reading. Your car with its AC on should always bring your fan to max cooling. If your car cant drop any temp to 185 or so with the AC on you have a cooling system issue.
Also,...many tunes especially SFR's cripple the low speed fan operation for some reason.
Boosted, tuned, E85 tuned cars in stopped city traffic should always use the AC as a fan switch and keep your car under 194 F.
Also, oil coolers mean proper temp oil, mean more efficient cooling.
Add to that if your are AT, cool ATF is almost a better engine cooling mechanism than the coolant. Together you have one engineered system in any weather.