I have a friend at work who owns a 2013 gt500 and he refuses to touch the pulleys or motor. The car completely stock(even stock tires) tops out at 190 and it's been tested several times on some really long stretches here in central Florida. So, I don't see how it can be so hard to do a pulley change, full exhaust, tune, etc and get one past 200 mile mark. If I'm not mistaken, there was an article online were this was put to the test and they came up with top speed at around 190 on their test car too.