What can be changed to the exhaust while still being able to go through technical inspection?

This only concerns countries where these technical inspections exist of course. Generally, SUPERSPRINT supplies homologation certificates that are accepted at the technical inspection centers providing that cats are not changed and that central mufflers are used (so use of resonated versions). If we really want to improve sound and performance, this is not enough (as you should use a non resonated version and downpipes + sport cats). Unfortunately, no supplier will supply homologation certificates for these mods and therefore it will not pass technical inspections. In France, the inspections are not as strict as in Belgium and they will be accepted providing cats (even sport cats) are used.