hey, i have the god speed rad as well, i now have all of my gauges working and running well.. now my setup is a bit diffrent, but wile doing research on how i was going to set up all of my circuitry, one thing i kept running into was this: OEM t-stats do not open up untill 190-200 the 180 i got was one of the lowest e-bay ones i could find. if you go with mishimoto, TRD, or any of the more reputable manufactures you will still have a hard time finding a T-stat that will go any lower than it first craking open at 180.. also there is the rate or speed at which the T-stat opens... before i installed my newer t-stat, i tested my used OEM and the new e-bay one side-by-side.. in boiling hot water then ice water, and back... what i found was that the e-bay 180*DID open sooner, but the speed was pretty much the same as the OEM, so that both units would be wide open at pretty much the same time...
also.. there is this.. the fan switch that is used to activate the rad fans, is a temp probe that closes the circuit at a certain temp... now what i found (IIRC) was that there was about a 30* spread.. OEM T-stats opening at 190* and fan switch operate at 220* this is done done so that the fan are not always on, and only turn on to keep the car from overheating.. this is why when your car idles the fans kick on and off every so often.. now here is what is different about my set up though... i have an ST and on the rad is made for GT/GT-4 meaning there was an empty port at the bottom of the rad.. i decided to plug that port with a a cheap Harbor Freight temp sensor/gauge.. this being that the temp readings would be reading the temp of the water after it hit the rad, and before it goes into the motor...
so.. i have temp of water going in, we have t-stat controlling water flow to the rad that opens and closes its opening based on the temp of the fluid hitting it, and the fan switch that closes at only a certain point...
this gives me a very odd but insightful view of what is going on in this process.. untill the car is warmed up, and wile driving around my HF temp gauge is pegged to the bottom of the guage, pretty much useless..... BUT!!!!!!!! when im idling i can literally see my oem temp guage (like all of us) climb.. and then see my HF gauge climb as the t-stat starts to open, then at just a bit over 200* the fans will kick on.... and then watch my temps drops on the HF gauge....
this is all allot faster when i have been driving and then come to a stop.. all in all a nice and easy way of seeing that the rad and the rest of the system is doing its job..
now you are reading your temps for your gauge at the top of the water flow.. reading engine temps.. great.. but you gota think that the pump is still pushing some flow into the rad, and the t-stat may still be working right.. just barely holding the port a bit open at the temp the coolent is sitting at. And with the bigger rad,, the heat soak is going to be slower, meaning more time b4 the fans kick on. and seeing a temp of 190* imo is perfectly normal.
lastly i have to ask, but am almost sure of the answer.. did you keep any of the OEM fan shrouds or did you just put the two fans up against the rad w/ the supplied push through clips?
i chose to adapt the main fan's OEM fan shroud so that the new slim fan fit inside the OEM shroud. i did this for one main reason.. function.. the reasoning for a fan shroud is so that the fan can pull air through a broader surface area than the diameter of the fan itself.. remove the shroud, and you are removing overall efficiency of the fan ability to cool the rad.. stack that with the fact that the new rad has more than twice as much thermal mass to remove than the OEM rad= slower temp drop rate... meaning the fans will be on longer..
so a 190* operating temp now looks very normal.
when i finally get my project thread i will have pix of all of this.. but till then i hope my description will suffice..

hope this helps some.