No matter what exhaust you have, what car you drive, unburnt fuel or not, if the car has been running for 15 minutes its going to be too hot too touch with your hand
Unburnt fuel should not really affect the heat of your exhaust. If you're running really rich, your car may backfire on full throttle or gearshifts and you will hear a POP sound. Also, the smell issue as Eug mentioned.
Also, why is this a concern for you? Unless the exhaust is making funny noises or glowing red I doubt its really an issue.