[91C2wrencher]

'96conv, LSD are always an option as they serve a specific function that not drivers want or need. An "open differential" allows only one wheel to spin(that being the one with the least traction) this is good for daily driving in moderate climates and provides a reduced stress on the drive train, particularly in tight turns. A LSD provides drive to both wheels and is desired in high performance cars to get the power down and aid in decceleration control(60/40 or 80/20 LSD reffering to the amount of slip between the two rear tires during accel. 40 and deccel. 60 slip). FWIW an open differential cars rears wheels will spin in opposite directions if checked while both rears are off the ground and one wheel is turned. A LSD rear wheels will turn in the same direction.

Dyno testing - put your car on a stationary dynometer and run it through the gears to measure hp and torque. No it not usually part of a PPI and usually never done except to verify engine modifications.