here is a nice video about the overreving problem (it's beacause of the time needed for the blades to reach the new angle) :
http://www.youtube.com/watch?v=psYL7...112BDB5C43E0E3
As tintifaxl said check that your mixture lever is on the rich position (the lean position is for high alt cruise)
Move the throttle very slowly to avoid overreving and keep the boost needle below +4.
Avoid negative G.