Stutter when accelerating hard 5000-8000 rpm range

[Gnasher]

Thx for the reply Pieeater. I also replaced the air filter so nothing is obstructing the air flow.

As to 'replacing the gearbox' or gears. Do you reckon it's possible to do this? I mean, i have enough time to do it myself. Read somewhere the engine needs to go out. Most people recommend just replacing the entire engine block.

Can any new spare parts be bought somewhere to replace the damaged parts? Or do you recon an entire new gearbox or engine block must be bought second hand.

Greetz

Yes it's a fairly straightforward repair, providing you know what you're doing that is and have all the tools.  First you need to confirm it is indeed the second gear driving dogs and to do that you've got to pull the engine out and split the cases.  From there you order the parts required and rebuild, i think there're modified gears available, but not certain you need to do some research. 

Or you just replace the whole motor,  quicker but more expensive maybe, choice is yours. 

Best of luck lets us know how you get on.