As far as I know, the canned Lvl 2 and 3 tunes modify fueling, timing and probably other parameters that effect how air is moved through the intake.
Because air is moved through the intake in discrete "pulses", each time an intake valve opens, there are pressure waves created that can reinforce each other at certain frequencies and these create the "drone". The helmholtz resonators on the stock intake are designed to cancel these out, even when they occur on a "tuned" engine.
The commercial CAIs were also designed for stock tunes. Anything that modifies the intake timing, is outside their design parameters. When Bill adjusts the tune to get rid of intake drone, it's my understanding that he sets the intake timing back to stock.
All of these conflicting requirements have the effect of reducing the benefit of a commercial CAI.
Since the Gotts mod retains the stock design, while removing the "bottleneck" at the snorkel you don't get the adverse effects.
- Jack
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