Check out CarTest/CarTest 2000. CarTest is a free DOS program that will allow you to input data related to your car, most if not all of which is findable on the 'Net and in your car's manual. CarTest 2000 is a non-free Java app that does the same thing.

That thing being run simulations of your car. It takes gear ratios, displacement, wind resistance, etc. and produces an amazingly accurate representation of your car which can then be used to find the best shift points for your car for certain circumstances (0-30 might be different than 0-60, for example), amongst other things. Quite a cool program.

I'd do it myself except for I have no idea what year or version of Focus you have, so no way to collect the proper information. You need:

• Engine Displacement (cc)
• Engine Location (front, rear, mid)
• Engine Type (NA, Turbo, Supercharged, sequential turbo)
• Max HP (bhp or kW) w/ RPM
• Max Torque (lb. ft. or Nm) w/ RPM
• Compression Ratio
• Redline
• Gear ratios for all gears
• Final drive ratio
• Front, Rear, or All Wheel drive
• Weight (lb. or kg)
• Weight distribution
• Wheelbase (in. or cm)
• Tire width (in. or mm) (the 1st number in your tire size)
• Tire circumference (ft. or m) (optional)
• Wheel diameter (in. or cm) (the 2nd number in your tire size)
• Tire profile (the 3rd number in your tire size)
• Coefficient of drag (oddly often published spec)
• Frontal area (sq. ft. or m^2) (optional, but helpful if you can find it)
• Overall height (in. or cm)
• Overall width (in. or cm)
• Ground clearance (in. or cm)