Sky, I am still running the 2540s. But I suspect they are damaged in some ways now as I could hear them whistling. On the dyno, the peak power keeps on spiking up and down as the boost spikes as well. And there's always a sec or two before they spool at full steam at some rpms (some hesitation). I have checked the boost controller/actuator etc and they are okay. I think it's the shaft hitting the housing. But the power is still there when it comes.
Anyway, I have purchased a set of 2530s. I will start rebuilding the whole thing sometime this year, probably after the endurance race in August. I want better response around the corners/turns and about the same top end this time. That's why I hv opted for 2530s after some research and your advice as well. I will prolly ditch the 264in 272ex cams as well. I will prolly use a set of low lift 264s this time around. We will see how it goes.