Thanks guys -- I really appreciate your help!
M.B.Doc: The fact that Bosch uses new tips is the reason why I decided to go with them rather than having the originals rebuilt by a diesel service shop. The injectors were replaced when I bought the car at just under 200,000 miles; not for any particular reason other than overzealously thinking it would be a good idea just keep the engine happy (I need to practice the mantra "if it ain't broke don't fix it"). The fuel system is not contaminated with water nor algae, I have been using RedLine DFC or 85+ religiously, & Power Services additive occasionally; the filters have been changed twice - once when I bought the car & again 3000 miles later (again, for no particular reason other than being overly zealous & thinkg that perhaps the additives may have disloged some crud in the system). The car now has 204,000 miles on it.
1. Were the injectors that you were rebuilding failing at 20,000 miles due to re-grinding the tips vs. replacing them?
2. Do you know if all Bosch injectors are rebuilt at the same facility, or at different locations, which could account for discrepancies in quality control?
Looking forward to your reply... Thanks again!