It's more believable, actually, for a MAF-equipped car to show improvement than a MAP-equipped car... especially as so many MAP-equipped cars nowadays adjust to any filter changes by dialling back power right away.
Air filter changes are like voodoo nowadays. We tested a MAP-equipped car with a short-ram and it made 5% extra at redline and nearly 10% less at 3k rpm (cruising), with AFRs going pig rich in the area of loss but slightly leaner (as you'd expect) at the area with gains. Even with the stock box in, replacing the filter with a less restrictive medium resulted in the same change.
Computers. Meh. They're too smart.
