Is it an intermittent misfire under load?
Sounds like a crook injector. Getting on and off the gas or splitting gears de-energizes and energizes the solenoids and if one of these are slow...
If it is a faulty turbo blow by should be low at idle and excessively high at hi idle with the little boost it will be generating at top engine...
Adjust your brakes, throw the maxi on and check your slack adjuster is straight up and down/90 deg as put earlier. If not and the other brakes...
A friend had this happen to him after getting a head done at 1 million km. Went 40k and spat #2 crown skirt and liner into the sump. Injectors...
