I agree with ya!
In our tests, as well, we found that 2400s will put out some faster laps, in the early stages of the race, but about halfway through the race they drop a bit while the 3000s just don't drop hardly at all (my fastest laps tend to be in the last 1/3 of the race).
At our raceway, 2000's work wonderful for 4 minute novice and intermediate races, but I, quite literally, lose almost a second per lap in the 5th minute. And this with very good 2000's that have been treated with lots of TLC.
RC10L2.5W - RC12.4 - RCNTC3(bmi) - TC4 (modded) - B44.2 - plus rent-a-rides! :D