RBF660 doesn't meet DOT5.1 as it is too thick. DOT5.1 has a very low viscosity requirement compared to DOT3 or 4. (Dot5.1 must be half as "thick" as DOT4)
It would also be a big indicator for anyone using that fluid in extremely cold weather to possibly look to swap for something in the DOT5.1 range.
Here is as close as we got to a direct comparison(3 vs 4inch exhaust), a tickle more boost, which I am sure was in part due to the exhaust.
Made 790 on more boost.
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