Might well be worth checking the exhaust manifold switchover valve vacuum pipe. The switchover solenoid valve sits in front of the egr valve to the far right of the engine bay. It has a (usually) white plastic pipe which runs to switchover valve at the right of the inlet manifold. If split or holed it will prevent the manifold switching to the longer manifold length and restrict your rpm and power as per your problem.
Hope this helps,
Tuesday, September 11th, 2012 AT 4:39 PM