I have mentioned before how sensitive the fuel system appears to be on these cars. My guess is that you introduced a fuel or compression leak during the installation of your injectors. You may want to pop the injector cover off and inspect for fuel leaks. If you fill the injector holes with water you can also see if you have any compression leaks (you'll see bubbles around the injector that's leaking compression). The injectors do need quite a bit of torque to seat properly.

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2004 VW Jetta TDI (manual)

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