I dont know if this is the one you have found but I use this and it works well enough
c= car
vx = velocity c select 0
vy = velocity c select 1
vz = velocity c select 2
nv = c setvelocity [(vx * 2),(vy * 2),(vz * 1)]
c globalchat "Holy crap!"
~1
nv = c setvelocity [(vx * 2),(vy * 2),(vz * 1)]
~1
nv = c setvelocity [(vx * 2),(vy * 2),(vz * 1)]
exit
Its simple but it works. Just addaction to your car like:
car addaction ["boost","nitro.sqs"]
and name your vehicle car. You could make it more complicated so that it would increase your speed over a period of time. If you want the car to go faster then just change the 2's after setvelocity to what ever you like. Hope this helps.
EDIT: now that I look at your post again this probably wont be very help ful
but oh well.