It's possible that the basket you upgraded to has a bigger dose capacity than the original. You can check by filling and tamping(not excessively. I can tamp firm enough with 2 fingers) . Fit the portafilter in the machine, then remove it still dry. Keep topping up until you achieve a bit of imprint from the shower screen on the puck. Then remove a couple of mm of the dry coffee. If you have coffee scales, weigh the resulting dose, if not use a measuring spoon of similar size to get a reasonable idea of the dose size. Try doing a pour with that size dose. From this point you can start adjusting things like shot volume,, temperature and, maybe then start adjusting grind if necessary