Just done it....
Took the top off my airbox and took a 22mm drill bit to it. A few strategically placed airholes later and my ST2 is now producing 140 bhp at the rear wheel and wheelying off the throttle in fourth gear.
Well, I lied about that bit, but...
It definitely makes the bike more responsive, it pulls higher rpm in top than I've seen before
and it makes a luvverly noise.
Not bad for 15 mins work and it cost nuffink