With regards to the SACLAM unit, it looks to me as though the HUGE resonators up front are what cures the drone, and the extra piping out back prevents the loss of backpressure.
Now, the HKS unit shown above looks like it serves both purposes by incorporating a "dead-end" with a resonator attached to it.
Also, backpressure isn't bad if its used correctly. For N/A applications, you need backpressure to prevent the loss of torque in free flowing exhausts. If you have too much though, then you will lose power. Think of it as a glass of red wine a day. In moderation, its actually good for you, but in excess its not. Horsepower and torque are both important IMO, and not just horsepower.
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