It does not matter whether the drive 3-4-5 gear. After 3000rmp system displays engine fault ..releasing the engine speed error disappears..The first and second gear is okay..
hmm...may need more info, but, start by unplugging the MAF and go for a drive. If its better, then its the MAF. If its the same, we move onto other options...
Have you driven through any standing water lately? If so, it could be a flooded overboost valve. They are situated very low down on the vehicle and are sometimes subject to water contamination. Do you have an undertray fitted?
Search the forums for overboost valve relocation. Alot of members have moved their valves higher up in the engine bay to avoid this happening. They are relatively inexpensive to replace if it is knackered.