In the summer I replaced the splitting muffler on my 4cylinder Ranger with a Thrush Turbo. It was partially as a joke.
I remember Turbos on V8 cars getting gradually louder over time, but on the 4 it seems to have hit a 'loudness limit' of some sort. At first I figured that maybe it was a lesser volume of air, but in all reality my 2.5L 4cyl is about the same as half a 5.0L V8 with dual exhaust.
Something also odd- On V8 cars I remember the Turbo muffler being quiet at low RPMs or a cruise with no load, but then 'opening up' and getting loud when you put your foot into it. The one on my truck is just the opposite- noisy at idle, half as loud at cruise, and when I put the pedal to the floor it is completely silent!
Bizzaro!
-ph