Sounds dumb, but try a set of Elixir strings. You might not like it but it will sound different. They work pretty well in my opinion.
Do you know if you have a good setup? A bad setup (too low or too much relief) can kill your tone (not to mention intonation but you didn't say that was a problem).
Someone already suggested swapping out the complete wired pickguard from a known good guitar. If you've got a buddy with a strat that could help you out you could quickly isolate to electronics vs. mechanics.
If its mechanics, you've got a lot of parts to play with. Check one thing at a time. I'd start by blocking the trem (do a search for how), changing the springs (or number of springs).
After that there are just too many other possibilities. Others here have thoughtfully mentioned possibilities.