How many miles of highway driving can I squeeze out?

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you should easily hit 300-330 miles on a tank

You're soon to find out for yourself, ain'tcha?

I would get around 380-400 miles on a full tank in my 89 FI but you should get around 340-360 mile depending on how fast you drive.

With an egg under your right foot and a MT, you might be able to pass 500 miles on a tank.
I did it once without the egg.