club.liberty.asn.au

It's a 2.0L GT turbo but has a Dash from a 3.0L GT.(I suspect going by the following) So first problem is the tacho reads around 4700RPM at the rev limiter(actual engine speed is around 7500RPM)
Other problems- Cruise doesn't work and the trip computer doesn't work(no KPL etc)

So, how did they get a 6cyl dash to work in a 4cyl? and why???
will replacing the dash with correct dash fix the other problems with the cruise and trip computer????

More likely that your vehicle speed sensor is faulty, limiting max rpm
Does it still idle at 6-700 rpm?

Tacho is out and will be 2/3rd of the 2L as the Tacho expects 6 pulses for every revolution. Your only giving it 4 on a 4 cylinder so 7500rpm is 30000 pulses, which is 5000rpm on a 6 cylinder tacho. Should be 4800rpm since 2L is 7200rpm rev limit but the maths is easier in my previous sentence