When you say "tuned carb", are you talking about an upgrade over the stock one or one that someone has already done tuning on? If you're looking for an upgrade, I've heard the one from a Losi 3.4 will really wake a 3.3 up so it should work on a 2.5. If you're looking for one that has already been tuned, your wasting your time because every engine will be slightly different.