While this is all true, I'd start with a resonator delete.
Drive it for a while, and see if that works. If it causes some unpleasant drone, put the resonator back, and try some muffler or other.
The base 1.6 has a compression ratio of 11:1, so it won't sound ratty. You want a deep tone that doesn't cause drone when you're cruising.
What that would be, I don't know. It should sound like this: FF to 5:13.
FF to 5:13.