This topic is loaded.
My first bit of advice for losing weight is lose the Thudbuster and purchase a carbon fiber seat post and get a professional fit.
I've done wheels, belt drive, carbon fork, and stoker carbon seat post.
By far the biggest change (and inexpensive) I could tell immediately was new tires. I'm guessing you have the 28mm Conti gator skins. Heavy, strong tire. I replaced with 25mm Schwalbe ZX and boy is there a difference!
I will be the first to say the 'skins are practically bullet proof (with over 3,800 miles and no issues), but I absolutely love how the ZX makes the bike feel.