Here is a link to the KRA Current Retail Selling Prices list that's used to calculate duty on motor vehicle imports into Kenya.
This is from April 2008, dont know how much its been updated since. I got it in January or February 2009.
There's a snafu on the BMW section but I'm told BMW CRSPs changed drastically with Bavaria Motors entry into the Kenyan market so probably best calling KRA for those.
I posted this because I find it stupid to keep the list a secret. KRA would have people believe that duty is charged based on CIF (cost, insurance, freight) of a vehicle to Mombasa. I have found that this is often a falsehood. I have also found that in many cases, duty calculated based on CIF is lower than that calculated using devalued CRSP, especially for newer vehicles.
To calculate duty, take the value of the vehicle you have in mind to import from the CRSP list and plug it into the Duty Valuation Template which is downloadable from KRA website here. The duty valuation template is pretty straightforward and shows what to key in based on age and type of vehicle. The spreadsheet should give you an idea of what your duty payable will be.