when im driving under normal city km/h limits, im fine but as soon as i hit it hard and the car goes beyond the 90+km/H i smell like its not burning off all the gas and u can smell it quite badly, any ideas on what to look for or fix?

its an 97 GST

just turn the boost up to match it!!!!

i would start with changing your thermostat, its a cheap fix, and it only take about 20 min. if it persists i would start checking out some of the wiring, from the temp sensor to the rad fans to make sure there is no short circuits.

An exhaust leak can also make you smell gas, especially if you are running a tad rich.
With an exhaust leak prior to the O2 sensor, you could expect the reading to be lean therefore the ECU adds extra fuel (in error).

Shawn's point on the thermostat is valid.
If your ECU does not detect operating temperature, it will be stuck in "warm-up" mode (rich).
This case is best checked with a logger as you can tap in to the ECU's coolant temperature sensor. I beleive there are some manual tests for this as well, try seraching with Google.

What about your O2 sensor?
If that's broken you'll run rich as well.

turning up the boost? is that a serious sugestion or sarcasm?

im going to replace the cheapest parts first such as the thermostat.

as for the O2 sensor, is it hard to replace and how does one know if its not working right?