Actually, performance should be on par with a P-51D. The PT-6 variant used on the Tucano puts about 1,600HP to the screw, vs 1,400-1,700 (WEP use depending) for the Packard Merlin on the 'Stang.
Also, the Tucano has an empty weight of abouts 7,000lbs, compared to 7,500 for the P-51D, with a similar wingloading between them. Both aircraft also have a similar max takeoff weight of around 12,000lbs.
The one place where the Tucano suffers compared to the Mustang is in-built weapons, sporting only a pair of .50cal guns to the Mustang's six-pack, though the Tucano can also sling additional .50's and 20mm gunpods. This all assumes a straight gunfight of course.