Brief bit of history, 03 STi, started at 350bhp now at 450, snapped first shaft at 350 with a reasonably hard launch at elvington, replaced with standard shaft. Power now up to 450bhp, went for an outing at the pod and I couldn`t get it to launch at all, so after speaking to Paul, I realised if I held my foot to the floor it would hold at 5Kish rpm and build 6psi, sweet. So tryed this out just, first try, clutch smell and still bogged, try again, Bang, other driveshaft gone.
I`ve got some DSS shafts to go in, but didn`t think It should be snapping em so easy at this level, is something else wrong?

 

what type of failures?
if splines then probably engagement length issue, easy to mess up if you have adjustable length suspension arms.....