you are right bluereiger, there is no noticable difference between 121 mph and 120 mph, but they are still slightly different.
but if you remember correctly, top speed was not the only thing i mentioned effected by the drag wings create. i also mentined fuel economy. the effect on fuel economy is caused by the drag created by the wing. the more drag you have, the more force is required to move your vehicle. the more force that is required, the more gas will be used, thus decreasing fuel economy.
lets do some math and see if drag has any effect on you.
according to the ford website, the zx3 gets 26city/33highway for fuel economy. lets say the drag caused by the wing decreases that only slightly. lets say 1mpg, i believe that is fair.
now, lets see how much that 1mpg will effect you over the life of your car (lets say about 100,000 miles) i will be using the number $1.50/gallon of gas to calculate costs. that number is the average cost of gasoline in the denver metro area for a year (where i live)
fuel economy without wing: 26/33
fuel economy with wing: 25/32
gallons of gas used for 100,000 miles without wing: 3846.15/3030.3 gallons
gallons of gas used for 100,000 miles with wing: 4000/3125 gallons
difference caused by wing for 100,000 miles: 153.85/94.7 gallons
cost of difference caused by wing for 100,000 miles: $230.78/$142.05
so, according to this math, installing a wing on your car will effect you. i have checked and rechecked my math and i believe it to be error free, but i am not prefect, please feel free to recheck my math and correct me if neccisary.
can you now see what i mean when i say wings effect your car?