do they click when taking up drive? We had a similar problem with the volvo. Where the spline on the driveshaft was fractionaly too small for the hub. This inturn made the shaft move a tiny amount and caused a clicking sound. Mostly when taking up drive and under hard acceleration. I have seen this problem alot on the k20a forum and always wondered if it was the same problem. My k swap im using karcepts hubs with oem shafts so hopefully wont have this problem.
For the fix on the volvo we used metal glue on the splines which works every time.
theres also ekk1 or ekk2 shafts. make sure everything matches!
i have clicking with my dss 2.9 too but think its because im running ekk1 shafts with dc2.
so i have brought some ekk2 shafts of weasel, hopefully it will resolve the problem...
This was a typical problem with DSS axles and i can't believe they haven't fixed this issue after all these years. Just do a search on k20a.org and you'll see all the problems going all the way back to like 2005. I'm almost certain it's due to incorrect axle length but i could be wrong. The only other reason they'd click is if your boots ripped and there isn't any more cv grease to lubricate the joints.