Loss of power
 

Hi any one got any idea's what causes my wrx 2004 to lose power when it hits round 4000 revs it runs ok untill i put my foot down then just dies?

Have you checked your boost and vacum pipes for cracks etc? With the cold weather we are having it may have caused a brittle pipe to crack or break etc maybe hope you sort it

As Zany said, definitely sounds like a boost or inlet leak. Check the inlet to turbo pipe and turbo to intercooler for any splits first, but it could also be the pipes to and from the boost solenoid and re-circulation valve.