Yes, you typically see the ability to put out more power for athletes who live at altitude coming down to sea level. It's usually the same increase as the decrease for athletes doing the opposite, so you can use the tables here
for reference. On those charts (using the acclimated number) the average person would be able to expect a 6% increase in aerobic power at sea level compared to 1600m. That would put you between .79 and .80 if using IF.
There are some issues though. First, this response is VERY individual. Some individuals will see a very small increase in performance at sea level, and some will see an increase much higher than those tables predict. Really, the only way to know is to test/race at sea level and find out. Another issue is that, if you've been used to putting out X watts for your 2.5 hour HIM ride, then putting out 1.06 * X is going to stress your muscles more. Some athletes living at altitude do occasional training sessions with supplemental oxygen for that reason (although living at 1600m this should not be that big a deal for you). You're also burning more glycogen at the higher power, so fueling needs to adjust as well. Finally, make sure to get down to sea level at least 48 hours before your start, to allow plasma levels to adjust, and of course stay hydrated.
I think the best way to deal with this (I also live at 1600m and often compete at sea level) is to learn to base effort on PE, calibrated with the PM. That way you're ideally able to do a well paced effort even without having gone down to sea level previously to test.