It would foam? Not just unburped air in the system from flushing it to put in water wetter? I havent kept track of it like I used to, but I have used "Purple Ice" before and it was fine. Havent heard of foaming.

How new is the radiator? Could be some blockage somewhere in the cooling system, that does sound a bit high. Also, what ratio of coolant/water? Snow and ice in Florida is flat out NOT a problem, so I run mostly water and just a bit coolant for corrosion protection anyways.

Radiator is maybe a month old? I can see coolant flowing well through the top fins when i have my cap off so I don't think there is debris.

But I am running a 90% water and 10% coolant ratio like yourself. Just enough coolant to keep it lubricated. I have purple ice but it foams on me, we tried it in my stock car and I tried it when I got my new radiator.

Not sure then really. That definitely seems high, and one of the first things that came to mind was some sort of blockage, or maybe a crushed hose.

The best route is to find out why the stock system isnt working well enough, but since youre in Texas, maybe it's just ------ hot out in the summer. I've been really looking into aerodynamics more nowadays, and thinking a good undertray and a reverse vented hood would be nice, even with a pretty stock setup. Apparently TSIs actually do a good job of cooling the engine bay, but pressurizing it isnt exactly smart.

Post up if you find out why the temps are so high though, might end up helping someone else in the future!

#1 Use a thermostat. Use a 185* if you want to run cooler than stock. Make sure the tickle valve is at the top to allow air to bleed out. Without a thermostat and without a reroute you aren't getting as much flow out of the back of the head and through the heater core. This may cause the rear of the head (where the sensor lives) to be hotter than it should.

#2 Your Miata will overheat without all of the bumper mouth plastic to force the air into the radiator, and all of the undertray back to the subframe is important as well. They keep the hot air from recirculating when sitting still as well, which is a big problem.

What are "stock temps"?? I have a begi reroute and going down the road I sit 180F

Do you have a 180F thermostat?

I have the stock 190F thermostat. At highway speeds my temps sit at 195F.

Edit: I see you have no thermostat. This is not a good idea. The thermostat does provide a flow restriction, which one might think is bad, but that also correspondingly provides a coolant pressure increase within the head. Point being the system was designed taking all these factors into account and removing that piece puts you in uncharted territory.

No thermostat is also bad for your setup. You need your engine to get up to running temps as quickly as you can, and that takes forever without a thermostat. IIRC, it'll also run richer to try to get it up to temp, which costs gas and often carbon deposits on the pistons. Theres more to it, but I cant remember off the top of my head

The stock thermostat is a double thermostat and is fully open ~193-195 degrees, iirc. It is discussed ad nauseum in a thread on this forum somewhere. The backpressure also assists the flow of water to the oil cooler which, as you might imagine, is a desirable feature.