Is your engine ECU the type which actually has a VSS pin? - if the ECU is from a later car that had ABS, it would have a twisted pair for the bus lines which carry data from the ABS, gauges etc.
If your engine is the metal intake 1ZZ from a 98 corolla etc, then it would be the old type as those ones had split lines for the VSS and ABS etc, the later ones had two separate kinds of ECUs, one with bussed VSS data and one with a direct pin for VSS input. (depending on the car if it was equipped with ABS or not)