Bullshit. It is a straight through muffler that will 'Y' into the twin tips.
I've had this on a 402 with a turbo, and with a F1A and made over 800 to the wheels. Throttle response was excellent, and still boosted over 20psi. I've had it on a dual into 3", and 4" to 3-1/2" to 3". The limit of the 3" pipe is what kills power, and/or bends that are short radius/kinked/or smaller than 3".
The muffler is completely at the back of the exhaust where the gas is the coolest, and restriction is minimal. Yes a completely 3" straight-through exhaust would make more power, but minimal gains, and this muffler is way more quiet with no drone. Don't bore me with bs numbers you have seen on a dyno.
This site, as well as RX7Club, has become absolutely retarded when it comes to people invading someone's sale thread. Let the person sell his goods and get lost.
If you need to know what 17 different people think of a product, don't buy it, just move on.