Pull the codes and look them up. Even without any check engine lights, there could still be codes present. Write the codes down, and clear the codes. Go out for a drive and check again for hesitation. If you still have hesitation, pull the codes again and compare. Find out what the codes mean. I'm not a 2GR-FKS guru, but have had plenty of BMW tuning experience, and problems with the HPFP (high pressure fuel pump) have always started with hesitations, then long cranking and rough idles. Could be something totally different. Hope I have been some help.