What about studies of 6000 to 10000 fu of nattokinase daily

The short version: no study in this retrieval tested 6000–10000 FU daily for plaque reduction, so the question cannot be answered from these records.

The retrieval contains exactly one study that tested a dose in your range: a retrospective, uncontrolled study of 1062 people given 10,800 FU daily (3600 FU three times a day) for one year [1]. It reported a 36% reduction in plaque area and a 21.7% reduction in carotid intima-media thickness [1]. But this study had no control group — it compared treated people only to their own baseline, which cannot separate the supplement's effect from natural variation, lifestyle changes, or other medications [1]. The same review also describes a 60-person trial at 2000 FU daily and a 30-person trial at 1500 FU daily, both far below your range [1].

The strongest evidence in the retrieval is a randomized, double-blind, placebo-controlled trial of 265 healthy older adults given 2000 FU daily for about three years [2]. It found no reduction in plaque progression or any cardiovascular biomarker [2]. That dose is well below your range, so it does not answer your question either.

No study in this retrieval tested 6000–10000 FU daily in a controlled design with plaque outcomes. The only study that used a dose in your range was uncontrolled, making its results uninterpretable.

My call: the evidence does not exist to say whether 6000–10000 FU daily reduces plaque. Confidence: not clear — no controlled study at this dose range was found.