Definitely not the Bike. 1) weight of the bike matters very little, even less in Palm Beach Florida (i.e. flat) And you actually have a fairly decent bike.
2) Lighter, more aero wheels, such as some Zipp 404's might make you .2mph faster , but its an extremely small factor, and doesn't explain your problem.
3) My bet is these guys that are dusting you aren't "Semi pros" or the "real deal". Likely just local guys, some of whom may race. There are a whole lot of people who can do 31mph on a bike. Not saying that the guys on your local ride aren't fast. I am saying there are a lot of fast people out there, that are way below the level of being a professional cyclist.
4) Keep going on group rides with guys that can dust you; you'll get faster in the process.
5) Read some books on training, (google Friel, and Carmichael) and start doing a plan with interval work.
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You could fall off a cliff and die.
You could get lost and die.
You could hit a tree and die.
OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.