Can you dyno a stock car non turbo with out chipping ? ??????
a dyno involves strapping a car to a dynometer and measuring the power output, thus any car can be dyno'd, in order to get more power things have to be changed/chipped/removed/added/whatever
so in your case you can have to car dyno'd to measure output and get say 100kw on the wheels,
then have the de-cat done,
put it back on the dyno and measure a increased output of say 103kw on the wheels..