My 4 does the same ,I feel that the mechanics can't keep up with human reaction or the other way around,especially spinning at 6500.
I have just had new input/output shafts and bearing in my box because I had no 3rd gear but the car drove like a goodun.
Whether it would benifit from a further upgrade in the clutch .?
how ever it just might be changing quickly and clutch not fully engaged ,hence the crunch.try launching in second ,or changing gear from 1 to third high revs .I did the 2nd to 4th and the car picked up mid range faster,sounds daft but it felt that way.