i also riding on Java Decaf TT. The tires is Chaoyang brand. If i changed to 451 wheelset, will it make a difference to the speed ?
Yes, but speed increase is only by a small margin, maybe at most 3-4km/h faster. It is not worth the money spend. By changing you stock 406 wheelset to a 451 wheels. you may also to need to change to a new set of brake caliper.