i think your thinking of the old schenke style water brake dyno's

as rollers are a set weight and and cannot be altered, its a lot easier to do it with the software than with carefully machining the rollers

i do not want to sound stupid here, but why is your car running lean under load, i thought you had just had it set up?????????
and no before anybody asks this is not a dig at anybody, i am just curious??????

why not turn the boost down a bit????? or the fuel up a bit???? or is there a mechanical problem elsewhere ????

pugo