the fuel pumps can be checked by checking fuel pressure. Check before the regulator and after the regulator. Check the duty cycle and eha numbers to see if it really is the AFM. That only needs the potentiometer as the mechanical part very seldom breaks. These guys look like replacers not diagnosticators. I would be wary of just replacing everything as this can get very expensive they can test all this stuff. Most of it is quiet easy now that steve has taught me how.
Good luck.
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)