In my pre, with a pretty large cap (2uf) right on the output, going to the vcaps was like turning on a fluoresce light.Did you give them adequate time to break in? We've got plenty of feedback that says that takes a while.
On paper, Teflon has the best characteristics of any dielectric (although at come frequencies polystyrene can be a little better, but polystyrene is all but extinct). So it should be no surprise that the Teflon also sounds better- lower dielectric constant, equivalent series resistance an so on.