Engine damage?

Hello dear community I have a new problem with my dear moose. Spark plugs I have already changed. To my problem, if I give gas in the 2nd or 3rd gear, so more than 2000 tours he starts to stutter, makes, I would say brum brum, noises and pull he does not want to, then jerks more. If I give gas in the stand he does not have the problem, so rather under load! Oh yes and in idle, the rotation number, varies between 750-900 revolutions, whether warm or cold, petrol it also consumes more! Oil consumption is normal but CO2 in the cooling water I could also exclude, by a test, the liquid remains blue. Thanks for your help!