Did you try running some Diesel Purge through the system or do an italian tuneup? How did you torque the IP elements? But I don't think that's where the fault lies. Hammering/pinging/knocking is usually caused by too much fuel being ignited at once which is usually caused by inadequate fuel dispersion and/or inadequate combustion temperature. Temperature would be related to compression and there's not much you can do about it if it's bad. But fuel dispersion is something you can address.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL