I was reading this page on TDI injectors:
http://www.myturbodiesel.com/1000q_how_to/multi/TDInozzleFAQ.htmIt says "The 1996-2003 TDI use a 2 stage spring fuel injector. The first stage is a pilot injection which serves to soften the pressure waves from combustion. The main injection is where most of the power comes from."
I own a 93 Audi 80 with a TDI. It's Euro-spec, sold in Germany. I have noticed it clacks quite a bit more than your typical US-spec 96+ VW TDI.
I'm wondering if maybe it's because it has a single stage injector?
I'm thinking about buying some US-spec injector bodies to quiet the engine down some.
i dont think your 80 tdi is single-stage , you my just need your pump timming done , or nozzles