I missed a few 2-3 shifts recently at a track day...I would definately say it is the timing for clutch release more than anything else. (My clutch hydraulic line blew out about half way round the lap i began having troubles, (Kinda scary whilst drifting around a hairpin, having to upshift to 3rd due to that low redline, and then ending up inbetween gears with another car inches off your bumper!)) Replaced the clutch line with a nice braided line and no troubles since.

Would also agree with one comment above about the shift points moving under load inversely to the direction your shifting in. 3rd feels like first, and 5th is closer to where 3rd should be when under full load (7-->8k shifts..)