@ Steven Raith
When you decrease the back-pressure in your exhaust, you have to increase the fuel-flow on the intake side of things to compensate for the increased oxygen flow into the combustion chamber. If you don't, you will be running VERY lean, which eats valves.
Your car, like most modern cars, is already in a "nearly too lean" condition from the factory, in order to get better mileage. Thus the occasional subtle popping with the stock exhaust.
And no, the stock computer will NOT compensate for the increase in airflow. It's not designed for that kind of thing.
You need to change the EEPROM(s) and/or injectors/jetting and/or fuel pump flow (not pressure, VOLUME!) if you don't want major repair bills down the road.
Always cracks me up when the CluelessBikerBoys[tm] pull the baffles from their exhaust and/or install a coffee-can muffler and pop-pop-pop away ... until they need a major rebuild.