Newly rebuilt injectors can take a couple hundred miles to quieten down. If the pop pressure was really low, you may now have symptoms of worn/leaky delivery valves. The nailing can be quite loud at idle or low RPM, but go away entirely at >1200RPM.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)