Scary diesel emission testing

How do you guys carry out diesel smoke tests? The manual says to press the accelerator fully, quickly but not violently and hold it there following the DSM prompts. My DSM instructs me to do the same until it says release the pedal. In the last year I have had about 6 engines suffer doing this, four Focus's (sounded like valves hit pistons, rattled and smoked before settling down and running OK.) An Audi A4 (turbo failure and had to stall engine) and a Peugeot (revved OK once and then wouldn't rev beyond 2500, I think it had jumped a tooth or two on the cam belt) It's got to a point where I'm nervous about revving diesels but if I don't rev and hold sometimes it won't register on the DSM. I know a garage where they only rev to 3000 rpm and then pass or fail. I think this test is out of date now. If you test a VW or BMW it's almost certain to pass because they won't rev unless you disable traction control and hold clutch down which can't be done on automatics so the test method and result can vary from car to car and tester to tester.