Originally posted by turbo8u
the problem with inertia dyno sweep testing is that it only tests the acceleration of the motor and driveline, it doesnt have any load. so what typically happens is the acceleration fuel maps will read rich so the dyno operator or tuner leans them out as with the main fuel maps and once the car hits the street, the actual acceleration of the motor is much slower than when it was tested and it ends up being leaner. you want to tune full throttle on the street, then dyno tune. or better yet, load bearing dyno

http://www.dyno.com.au/home.htm