First Olympic tri in 2 weeks...

Any last minute advise for an Olympic distance newbie? I have done 3 sprint distances in the past but am worried about the long run at the end. The swim should be a breeze (usually first out of the water among women). The bike should be fine...though this is when people start passing me But I struggle even on a 5 K run during my races. It's not that im tired that much, but that I have trouble breathing (runny nose, asthma type symptoms). What's weird is that it doesn't seem to bother me that much when I run when I'm not racing.