the boost gauge shows that shifting 1-2 @ 6100k-6200k, 2-3 @ 5900-5800k and 3-6 @ 5800k is best.
Also, remember to launch around 4.5k-5.5k for best results, so that when the clutch engages, the rpm needles wont drop under 3.5k-3k (which is when the turbo starts spooling)...if it does drop under that range you will see the car will bug/choke and you will be caught in the turbo lag. Make sure NOT to dump the clutch, just remove you foot...someone said it takes a "mississipi 1"..which is between .8-1.0 second