I am a little confused

[blue4:2]

I have two ZR-1 -91 but they don`t behave the same, when i turn the power key on. Both cars reacts as they supposed to at about 3000 rpm and runs great ,Car #1 feels quicker and reacts faster and I have noticed that the car
revs according to the tach 2000 rpm at about 60mph at 6th gear and the other car revs about 1500 rpm at the same speed, My idea was that the

final gear was changed earlier in the cars life but after checking that out i was confused, When i turned the wheel one full turn both cars driveshafts turn 3 1/2 turns (the same) Can the tacho give the wrong numbers ?



Only minor mods are made to the higher reving car but the ECM unit is adopted from a 1990 Z (Thank you ccmano) due to a major failure


If you have any ideas please answer


Best regards from Sweden