Sorry to bump in on your thread, saves me opening a new one. I'm contemplating going to 3:45's as i have fitted the AU T5Z which has the 2.95 etc gear sets as opposed to the E series 3.3?, it doesn't quite feel right with the 3:23 diff, especially at 100k, it won't sit at 100k, it will cruise fine at 90, or at 120, but i have to keep my foot on the pedal more than i should to have it sitting at 100k, and it's doing about 1900-2000rpm at 100k.

Should i be sticking in the 3:45's to match the gearbox? Will fuel economy improve?

She has really long legs! Even the WOF guy who tested the car, took it out, came back and the first thing he said was "it's got bloody long legs".

with an Auto,
3.45s sit at about 2000rpm.
and 3.23s about 1750rpm.