Mikael, I am sending a pdf that may help one cog change on your cam should alter the system by 18 degrees.
I think you are right you are going to have to pull the valve cover and confirm your valves are opening when the should based on your engine and timing setting. There is something not right.
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)