dont you think 150 km/h for a 1.3 liter engine with an ancient gearbox and unnecessarily wide tyres is more than enough mate?
you need to consider elevation, wind speed, air density and wieght, otherwise given the real world conditions you speed is more than good enough,
my manual wont do more than 135 with 195 profile tyres
but still if u feel the need for speed switch to 175s, and slight downhill road you might go 170,