EVOs dont sound hollow. When you consider the range of tones of pickups from P90's to Single coils, EVOs dont sound that different then most other hot, ceramic humbuckers. Subtle differences at most.
I have every peice of gear he used to record that song. A Jem 7v. A Boss DS-1. and a Bogner XTC 100B.
One of the main things with that tone is there definitly seems to be more gain comming from the DS-1 then is usual with Vai. It sounds like the Bogner is set for a little crunch and the DS-1 is set with a lot of gain. From my years listening to vai It sounds like its usually the other way around. That can give you a really bright and edgey distorted sound right there.
It sounds like hes using an
Ernie ball stereo
Volume pedal so he can cross fade the dirty and clean amps. Its a really cool (but not new) trick. When he comes in dirty I believe he is still on a coil cut postition. With that much saturation you can get a single coil to sound like that. When he switches to the bridge at that one point it looses that hollow sound and just sounds like the usuall vai with thw wah and harmonics, blah, blah....
The cab, mic and mic'ing technique has ALOT to do with getting sounds like that too.