^ Hi thanks for the info my bro fixed his rad one time in his EK. So he has experience I will show him your post so we can work on it.
And yes if you kick down plenty and in vtec mode the Engine over heats quickly.
The needle in the dash reads quite hot. The mechanic took out the part with the valve thing. He say that sensor not good and its only used for heating the engine quick from a cold start since it restricts water flow. He pelt out that and it did nothing to the problem. He charged me $60 for that, I won't be going back by him again.
But if you don't kick down and constantly in vtec mode, it will over heat but will take longer. In vtec mode the needle reaching red hot.
I carrying this by a radiator man to find out the situation with this. If it work for a year well I could live with myself since i get some form of service and buy a SIR radiator like you said. But as it is this car can't go more than 3 miles without overheating.
Carrying it by the radiator man to do as you said and will post a feedback on what took place.