Preparing for my 90km cycling in Singaore 21st March 2010, need some tips on speed work?

Sounds like you are doing a lot better. Keep riding as much as you can. You can try picking up the pace a little more towards the end of your ride to get stronger. I noticed when I started climbing the steep hills I picked up more speed on the flats. You can also do some intervals where you go at a very fast pace for 30-90 seconds and then drop back to recover. You won't be able to ride as long but it will make you faster overall. Drink a protein shake as soon as you are done, it will help rebuild muscles. Eating a bunch of carbs the day before will help build up your glycogen supply and you will see a difference in your performance. You know how to go the distance so work on your speed with shorter rides.