I guess I don't quite understand why it would be impossible/impractical to make a N/A Leggy rumble. It's not the turbo that makes the rumble, All the components that make the rumple are there, and in the same layout, the only difference is the exhaust... The car will just be missing the notable "Turbo" sound.
The turbo won't make or break the rumble. My 92 rumbles to the point I get comments about it when I take the muffler off.