Gain muscle and still run 2 miles in 13:00...plausible???

Interval training is the key to speed.

Joe(go go)Nation

Thanks for your help.
you mean something like 60/120's.....sprint for 60 seconds rest for 120.
or do you recommend a different variation?

There are all kinds of variations, J. You're trying to two miles faster, right?

So, maybe start with quarters. Warm-up with a mile or so slow slog, then run a quarter at a pace just a little faster than your normal. It would be great if you had a measured course to do this but if you don't just run steady and watch your time. At the pace you are running at now, (15:40) it takes you about 1:50 to do a quarter.

Check the time. That's your quarter.

Now run that quarter in a minute and 40 seconds. You're not trying to kill it, you're trying to go faster than normal.
Run steady and strong all the way through picking up the pace at the time to meet the time.
Rest two minutes.
Do the quarter again at 1:40.
Rest two minutes.
Do the quarter 1:40.
Rest Three.
Do the quarter.

Four or five intervals is plenty. Six, if you are feeling really good.

Two days from now you are going to do the routine again and next week maybe shave another five seconds off the quarters. See how you are feeling. Do intervals at least twice a week in your training, shaving just a little off the times as your body tells you to.

What you are trying to do is get the feeling of what running faster feels like. Four or five weeks of inserting these faster distances into your routine and you will see that on the longer runs the quicker pace has become your normal.

intervals can be any distance. Mix things up. Do quarters one time and half mile intervals the next.
(Hey, would that mean I would be running five or six half miles?)

Yes. You don't learn to run two miles faster by only running two miles.

Here a site where you can log your intervals and any other running you do . Running Ahead

Joe(now get out there)Nation

Wow, you've been more than helpful.
Till now I've just been running two miles everyday.

I will implement this immediately, sounds promising.