I finally got around to de-catting the rest of my exhaust...
all measurements taken 1 meter away (around 39") from the tip directly in line with it... "C" weighted & "slow" response...

-the before-
Gutted uppipe, stock DP, stock 3rd cat, & Borla cat back.
Idle - 100.5dB
3k rpm no load - 107.5dB
5k rpm no load - 104.0dB

-the after-
Gutted uppipe, Stromung cat free DP, 3rd cat eliminator, & Borla cat back. (a full 2.5" turbo back)
Idle - 99.75dB
3k rpm no load - 111.0dB
5k rpm no load - 109.0dB*
*on letting off the gas, the exhaust "rapped" or "burbled" to 116+dB (very tough sounding)

The general popping or "after fire" is much more prounced, the exhaust has a very hollow sound & you can hear EVERY little thing from each exhaust pulse, to the turbo spooling.

 

The gutted uppipe realy doesn't make a bige sound diffrence...
so the louldness listed in the first set of numbers is pretty accurate.
To enjoy the Borla on a WRX you have to like lould exhaust inside & outside of the car...

It can be a little drone prone at times & even with the stereo up, you know the car is running...
You do get used to it...

I'll get around to some dB measurements in car as it is now (no cats) & see if it is at least at a safe level for long drives...
It isn't to bad in the car, but realy lould directly behind the car...

Osha has some charts on max time at a certian level before damage can/will occur...
basicaly...
85dB - 16hours max
90dB - 8 hours max
92dB - 6 hours max
95dB - 4 hours max
97db - 3 hours max
100dB - 2hrs max
105dB - 1hr max
110dB - 1/2hr
115dB - 1/4hr
120dB - 1/8hr <---that is 7 and a 1/2 minutes

as far as HP gains... maby a little. Thats just me though.