what is a throdle sensor?

A Throttle Position Sensor (TPS) tells the computer how far you have pressed down on the gas pedal. A malfunctioning one could cause all sorts of problems. If your check engine light is on, you should go to the auto parts store and have them scan it for free to see if the TPS is malfunctioning.

"Go into gear"? Do you have a manual or a CVT?

Subaru's rev high on cold start once it's started wait a minute rev it up manually and watch it drop to normal rpms the transmission complaint is normal operation they a very delayed when switching gears especially from reverse to drive. I've noticed if people have never owned a Subaru before they have a hard time adjusting, don't be frustrated or worried I assure you that is normal.

Again, we're not sure that's what Guru92's question is asking....