I've hit a drive 434 yds. in Career mode after playing for a couple of weeks. Here's how I did it.
Max out your character to 100% in all categories. Get 4x bonus accessories to boost you to 110%. I have all but power boost (which is at 3X/106% and is unlocked after you drive 100% of fairways in a round). I maxed out and got the bonus accessories through playing the Tiger Challenges.
I can't remember which hole I got the 434 on, but it was teeing off of a high elevation with a gale force wind behind me. I used full power boost (tapping "A" during backswing), and let it rip. FYI, my 9 degree driver is rated at 312 yds, and on an average fairway without any wind or boost I hit around 320-330 (usually adding some topspin during flight). With some wind/ elevation/boost, 360 yard drives are routine. Of course, the further you bomb it, the more your accuracy suffers. I hope this helps.