Injecting water before the turbo will erode your compressor wheel. To spool up quickly they make the wheels out of light weight aluminium alloys. These alloys are not very durable. I can't imagine the small bits of the wheel are very good for your engine either. Relocate the injection point to a spot right after the turbo.
The pinging or knock sound could be due to injector pump timing. Timing chain stretch which can throw the injector pump timing out of whack. Increased load on the engine might aggravate this to some extent.
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