I have a 96 wrx wagon. At what rpm is it best to change gear in order to go the fastest. As when i thrash the gears to say 7 the car seems slower than if i chage at 5.5 6 rpm?

 

Sounds right, torque curve will be on its way back down again. The curve will vary from car to car and under different conditions. Have a look at some of the dyno graphs on here, find the closest spec to yours and go from that

 

Contrary to popular belief you will get best performance by changing up before 6k rpm subject to your actual gearing and mods which will determine actual change up point on your model car.