SR problem, no power until 4k after warm

[Cloud9]

I have had my SR for about 5 years and have maintained it well and been able to diagnose everything so far but i am confused on this and searching has not been helpful.

Engine SR20DET blacktop S13
Problems, Car runs great until it has reached operating temp. There after the car will sound as if it is spooling to infinity and beyond but it will make no power in the process. Once it hits (roughly) 4k rps the car will start to accelerate as it would normally (maybe a little less power)

Other info:
Car has koyo aluminum rad, flex-a-lite fans, new water pump, but i only have a stock temp gauge but i dont think its over heating.

It isnt over boosting, or at least my gauge says it is normal. Its a stock T25 with hks actuator @11 psi peak

Other intermittent problems (maybe related)
On the highway when you hold the throttle steady the car will slowly loose speed/rpms, and when you give it just a tad more throttle to keep a steady speed it will jump up in speed/rpms/power as if you pushed the pedal down to make a pull. (hard to explain, hope its clear)

Well anyway thanks for reading and hope i was clear on everything. Will try all answers and will post results until i get a fix, thanks.

[NIZzS13]

Hmmmmm sounds kinda like TPS or Coolant temp sensor, maybe both. I would like to lean more towards the coolant temp sensor, they r know to cause major issues with these motors.