904 Flares on 2-3 shift?

My apologies if this has been thrashed out before,
But we have a 904, bought from a reputable shop. It's a full manual valve body "drag free" (What ever drag free means?) 904. Supposed to be a pretty good unit. According to the shop who supplied it.
However when I'm racing, and really have the boot up it it flares on the 2-3 shift. The obvious answer would be go back to the seller. but they're in the USA, and we're in New Zealand.
Plus I've never had bad advise on this forum yet. Trans has done maybe 1500 miles, and about 30 passes since it was installed two ish years ago. I'm starting to get the hang of driving the car now. so it's really bugging me. (I used to think I was knocking the shifter too far and hitting N, since it still have the column shift.

Thanks in advance.