RB25 hiccups after warm up

[mwt2573]

I have a series 2 RB25 and everytime when i start my car I it runs smoothe until it warms up. Once it hits normal operating temperature the car starts to hiccup every 30 to 45 seconds for about 20 min of driving and than goes away. Always begins as soon as car is warmed up at normal operating temp. Thinking related to coolant temp sensor which i had to unplug for car to start up (cold starts ok, but after initial start up wont start with coolant temp sensor plugged in) i bought a new temp sensor and same problem. Friend tried rb26dett ecu and car starts fine with coolant temp sensor plugged in. could it be my ecu???