I will give it a try but no garantees. The fuel comes in via the injector from the distributor. I would imagine if this is caused by the fuel system all or one rather than one side. However, the air side of the system souds like the culprit. You have a rubber hose that has 4 tubes that go directly to each injector this rubber can get very hard and crack. That is the first place I would check. It is a cheap fix (@$20 a side) if the rubber is hard I would replace it anyway.
hope this helps
m

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Martin Ingram
Colorado Springs
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)