Thank you for your detailed explanation. I wish I had seen this sooner so I could have included this in my decision but, three weeks too late. Considering I have noticed little to no difference in performance, I cannot say it would have made any difference in my decision.

Sounds to me there are only three options,

1. Accept the loss in torque for the improved sound. There doesn't seem to be a pre-designed exhaust to achieve both.
2. Stay with a stock exhaust to retain back pressure or replace with a lower diameter exhaust which will not likely achieve the sound I was looking for.
3. Build a custom (expensive) exhaust with the goal to achieve both.

Given all that, I would probably still have chosen the Adamesh and accepted the results, the sound is that good.

 

Yep, at this point, it's a little late to reverse the surgery. However, you might be able to regain a bit of the lost low-end torque by experimenting with different exhaust tips to add back a little restriction (which could give you an even deeper sound...).

This might be just snake-oil, but I'm wondering if a hard reset might help. There are some real experts on the forum that will hopefully jump in here and correct me if I'm wrong (or back me up), but retraining the throttle control module might help the car compensate for the lost low-end back pressure (or not, but what would it hurt?). Note: Don't do this if you have a smog check coming up tomorrow; it takes about 300 miles of driving before the various emissions modules will reset themselves...

Here's the procedure I use:

Disconnect the battery ground cable, and momentarily ground it to the positive cable (I use a piece of wire coat hanger to reach between the ground and positive cables). (Alternatively, leave the ground cable off for 20+ minutes to drain any residual charge.) Reconnect the ground cable.

Turn ignition to on (position II), but don't start.

Reset the windows ("roll" up and down individually, holding switch at each position until you hear a light "click" from inside the door).

With switch in position II, (not started), slowly depress the accelerator pedal down through the kickdown detent to the floor & hold for 5 seconds. Release pedal and repeat 1 more time.

Start engine, idle until operating temp is reached. Switch off.

Restart, idle for 2 minutes.

Apply foot brake, shift to drive, idle for 2 min.

Then, drive for 5 miles of varied conditions.

That's it. Good luck and let us know your results!