Hi, and welcome to the Blog! And nice job on the PR! That's a solid time.
Seeing that you've only been on the blog for a couple of days and so we can't see much of a history on your training, I can't say a whole lot, but here are a couple of things.
1) If you want to increase your speed in the marathon, once you have solid base mileage, I'd highly recommend trying the suggestions in this thread:
http://fastrunningblog.com/forum/index.php/topic,1076.0.html2) I'm sure you're figuring this out, seeing that you're getting into the sub-2:40 realm and seeing some big PRs (you're obviously doing something right!), but the best way to be a better runner is to run. I pretty much tell this to everyone that asks. Again, I can't see much of a history on your training, but in general I'll say I'm a big fan of just running...consistently. I'm still working at getting better and more consistent myself. Other activities can be helpful in some ways, but should not replace running or prevent you from getting out and grinding out the miles (unless there's a special circumstance like an injury). Running doesn't have to be fast all the time. You'll get faster just by spending the time on your feet running, along with your marathon specific training (see the above thread). You don't need much in the way of fancy training plans, supplements, diets, special exercises, lifting, or anything like that. The key is to consistently get the miles in, and then to target a portion of those miles to preparing for the demands of the marathon.
That's my two bits. Hopefully that helps!
