The MX-5s are very deceptive, especially once you fit a sports exhaust. They make all the right noises and with your backside 6" off the ground they
feel pretty quick with your foot planted and are
very nimble around corners.
I can assure you they're not anything special in a straight-line though - I drive a 400 bhp Evo on a regular basis, I wouldn't be surprised if it could keep up with a 1.8 '5 on straightish roads without even using the turbo!
On the other hand, the '5 does fly through corners at speeds that would have you backside clenching a bit in the Evo! Even with the additional cornering speed of the '5 though, the Evo would be able to overtake it on the first road that even resembled a straight.
I'd much rather be in the '5 with the top down on a late summer evening B road blast though!