1991 940GL live axle rear

I have a very annoying knocking sound coming from the rear suspension of my 940 sedan. Just before Christmas last year, I installed a new set of Bilstein shocks and I suspect the knocking is coming from these. All the bolts on the rear are tight including the shocks. I took the shocks out this afternoon and couldn't see anything physically wrong with them except that on one shock the sleeve on the bottom where the bolt goes through is not centred within the bush. I mean that the sleeve is poking out one side further than the other. I tried to even this up with no success. To me this really indicates poor quality control and I feel like taking them back to my supplier and telling them shove them where the sun don't shine.
The knocking sound is very noticeable over small corrugation and train tracks etc and is bloody annoying. I tried taking everything out of the boot to eliminate this possibility but no luck. I wish I'd kept the old shocks to compare. Is there any way I could confirm that it IS the shocks before I rip them out again?

Any tips would be welcome.

Brad