[ShoeDoc]

BPS: Purchased earlier this spring, just got around to installing it yesterday (Friday). My set-up: 1980 911 SC, completely stock rebuilt motor, transmission, suspension, gutted the interior & replaced. Cams are standard SC but "advanced"; exhaust system is stock with Cat delete. Sound absorbent materials in place, even replaced the head liner.

I can only estimate (as we've not done a dyno) but reasonably believe to be making approx. 210 HP. After installing the BPC with sound arrestor, I have to say the motor sound is just short of what a race car sounds like.
Whew! Admittedly, it is an intoxicating sound - complete with deceleration burbles, pops, gurgles. My "seat of the pants" dyno estimate is a nominal 10% HP gain - maybe 20 horses (?). What I can say is the RPM's come up substantially faster and without question the motor is breathing much easier.
Found myself pulling 5500 RPM's effortlessly and had to constantly watch my foot - the sound of the motor wrapping up plastered a huge smile on my face... had a one hour drive home from the shop and it's a screamer after 4K. Oh my... weak in the knees!

Now for the other side: It sounds like a race car. Would fit in wonderfully at Sebring. Living in FL means A/C and windows up; I can have a conversation with a passenger, listen to tunes on stereo, make phone calls and such.
I live in a semi-rural area - houses are spread out, lots of open roads, not much in the way of urban traffic or stop and go... no "concrete canyons" to reflect the sound.
That said, I still wish it were quieter; I came out of a stock muffler so I guess I have to allow for that as a reference point but the BPS - even with sound arrestor (I believe its supposed to reduce idle sound by 14db?) is LOUD. TOO loud.

I love the power.
I love the sound.
Love the scream of the motor.
Just not on a car that I drive every other day.
Track car? You betcha. Race car? Absolutely.
But, as things stand, I will remove it shortly.
However, I will also contact Bisi and see if there is any progress in developing an improved sound arrestor... 'cause if he can just get the db down, I could say without reservation, this is the least costly, easiest and simple 20 HP gain I ever had on any car I've ever run (I started 45 years ago with a '58 Corvette with a 283, but I digress.)

So, that's my take on the BPS... great device, well engineered & fabricated. Just a bit over-the-top for my aural tastes now.

ShoeDoc, aka, Bill in Florida