I do not have an answer on your last question but I have a 6MT and start with AWE + OEM downpipes and switch to AWE donwpipe and did not feel much difference .
I was tring to be quieter inside de cabine ,around 65 when you go up hill .It's not droning ,it's just louder .
It's also interesting how the sound travel in this car ,I don't know if you noticed it but the exhaust sound is different when you are on the passager side ....maybe because the middle resonator is below the rear seat on the driver side .




