Please do mention the slope angle where you achieved 180 km/h
My personal experience with my stock cultus 2003 VXR is
130+ on CNG on flat surface.
approximately 145-150 on Petrol on flat.
165 on CNG at Kallar Kahar M2 (that is on slope)
In my experience 185 km/h on stock cultus is not possible without a long sloped strecth of road, probably not even with 1.3L engine.
However I would definitely like to hear the details of your experience @hunchback5