A Question for all the experts. Vehicle speed sensor.

As some of you may or may not know i have re-engined my T4 Caravelle with an AHU engine from a MK3 Golf. Its all in and running fine but i have one code which keeps arising which is for the VSS which isn't connected. The reson its not connected is becasue my clocks use a speedo cable. My question is, does the VSS not being connected effect the running of the vehicle? Its always seemed to underfuel even though i have tried the hammer mod and vag com adaptions. It has a bit of a stumble from time to time at idle and just slightly above particularly when you blip it very slightly and particularly after its been driven at speed for a long period.

Any ideas? If it does i will have to keep a lookout for some Passat clocks which apparently fit.

Thanks in advance