high duration cams dont necessarily correlate with high top end power. nor does having a higher final driver equate to having better acceleration.

with your tdi 5th you'll be able to cruise at sane RPMs but the difference between 4th and 5th will be maaasssivve.

if you plan on going FI or big power, you should keep old ring and pinion because you'll want the taller gears to wind out. (as tim said!)

to make total use of the 288s.... you'll need a lot more than better gear ratios..