Is there any easy way so spot an injector induced knock? What damage can it cause if it goes uncorrected?

loosen the injector lines one at a time with it running. bad injector will stop knocking when loosened.

Can a knocking injector cause damage?

Cold fuel sqirting on top of the piston, not good, it will pit the top of the piston.

i have a motor that i took apart that i believe had this problem. was given to me it had 2 pistons that were eroded on the top outside edge all the way down to the top piston ring and the hole in the precup was burned almost round you could stick your baby finger in it-:t

Can a knocking injector cause damage?
Bad, very bad. In worst case scenario, a bad injector will not only cause damage to its own piston and cylinder, but the unburnt fuel can cause damage to adjacent pistons and cylinders.

Serious injector problems can not only endanger the engine, but you could sieze the pump too, DS pumps are expensive, try buying one without a core.

tdg why are the ds pumps so expensive without a core the cores are all over the place cheap i asked the fuel shop out here what my 5521 pump was worth as a trade in on a mechanical pump and was told nothing i have hundreds of them on the shelf this was a working pump that came off the motor i put in my truck as i went mechanical

The fuel shop business is HEAVILY dependent on cores. Everybody wants exchange units, so shops need cores to build for their stock. DS pumps are a strange animal in that reguard. Yes, cores are readily available for dirt cheap, but it makes more sense to collect cores from customers than spend time/money on 'new' cores. DS pumps have many more wearable or updated parts, and often times even when the customer does return a core, like a 5067, it has very few useable parts to build 5521s. It doesn't make economical sense to update one when you can just wait for 5459/5521s, which are likely to be in better shape anyway. Out of 10 customer cores we get back, probably only 6-8 of those ever get rebuilt, you couldn't make any money on them if you build every single one. Too many old or water damaged cores. For this reason, fuel shops have to take in a considerably higher number of cores than they sell.
Now as far as exchanging a DS for a DB, I'm not surprised at all, 6.5 DB cores (5088, 5436 and 4911 in particular) are a whole different animal and a totally different core market. Their cores are more expensive, more rare, and still in demand.