If the good throat hit happens after you've been vaping your 510 for quite a few puffs in a row, it's probably the atty primer you're feeling. That stuff's got amazing throat hit. If only it tasted good ...
The 510 has a much more effective atty than most e-cigs. It can burn off juice faster than the cart can wick it, so you'll find yourself tapping it on its LED end, or doing the "thermometer shake" to get more juice down to the atty. Or just topping off more often.