So, on the advice of an injection specialist friend of mine, I replaced only the leaking injector. Car runs just fine. No signs of the engine hammering on one cylinder, etc...
If one cylinder was hammering, he told me to replace the rest...

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All it takes for evil to prevail is for good men to stand by and do nothing.

Too many people tip toe through life, never attempting or doing anything great, hoping to make it safely to death... Bob Proctor

'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic