Pace different in training and racing

I think your training pace is probably about right for what your race pace is currently at. My training pace is usually between 9:00-9:45 but my last duathlon and 5K splits were between 7:30-8:00. I even pulled off a 6:50 mile somehow.

I'm the same way though, if I try to run a 7:30 during training it feels painful. I just throw in some speed work about once a week and trust that my slow running will pay off on race day. You can use the Mcmillian running calculator to give you a good idea for a training pace. 

It's definitely the excitement and feeling of competition that drives me during a race. 

I agree it's probably mostly adrenaline.

I am new to tri's, just started training 3 months ago and did my first event last weekend.

My training pace is roughly 8:15-9:00 miles but for the event I did a 7:30 pace and it felt pretty good.

I think it's a combination of tapering mostly and adrenalyn/excitement to a lesser extent.  If you're working out every day your legs are fatigued, so if you try running a faster pace its harder for them to hold that speed resulting in feeling like your gonna die.

Also, if you try to train at your race pace you will not be able to run as much or as often so its way better to run slower more often than to run fast and not as often.

I usually train around an 8:30 - 9:00 mile pace but my races are usually around a 7:30 pace.

Are you talking about the bike (instead of running)? I see HR is in zone 4, but where do you "want" the other metrics to be?

Typically I'll see HR and power track along each other with only some variation, after HR is given the time to catch-up. The variation can come from how well rested or fatigued I am at the time due to the training load. For me it hasn't been that significant though. If I'm tired, neither will want to go up. But come race day, both will go up noticeably higher for the same RPE. I'm able to push harder with the competition.