I'm surprised that you're finding the Swift slow!

In my experience, it has it's faults: biggish fold size, not that great to stick into/out of cars, occassionally tetchy derailleur holder. However, it is a very zippy and fast riding bike. It's not as fast as a dedicated roadbike, but is definitely comparable to a relatively fast hybrid bike in stock form.

I'm running Big Apples on mine. However, I've heard good stuff about the Schwalbe Kojaks and Marathons.

If you're still finding speed issues, try PMing Jur.
He's a pretty amazing Aussie, and one reason why I bought my Swift.