Stock B&S + Procharger makes all that high $, high RPM valve gear superfluous. The pumping loss (driving the blower) is really small at low RPM (unlike a Roots) and the milder low overlap cam has much better low RPM/high vacuum manners.
Extra feature: makes the complex, how-close-are-they-to-equal-length, what-RPM-do-they-tune-at headers expensive overkill since the blower flushes the chamber on every rotation without any exhaust signal. Just size the primaries for the power, not the inches.