Exhaust tuning

Was curious as to the parameters that need to be focused on when installing a full aftermarket exhaust? If for example, I'm running catted downpipe with a performance catback system, what are the tables/parameters/graphs that need to be addressed to tune the new system? Many reflash devices will include a base tune that takes care of that calibration, what if I am using an standalone ecu, or tuning for speed density where it isn't necessarily pre-calibrated? Thank you

Hopefully the Volumetric Efficiency will increase with your exhaust system changes, this normally means only the fuel map will need modification. However, if some fuel changes are large, then you might need to revisit the ignition timing as well.

Thank you that was helpful! Now what if you are MAF tuning, where the fuel tables become unavailable to adjust; and only fuel trims and fuel corrections and individual cylinder trims can be adjusted; would I only have to tune the ignition table as the ECU will aim for the targeted AFR ratios?