I recently bought a 2021 Cx 30 premium plus turbo with 5k miles.
I traded in the exact same trim level 2021 model.
the first car was absurdly faster on acceleration.
dealer has run diagnostics and hasn't found anything wrong.
what is possibly my issue?

 

Welcome to the forum

This is not unusual by any means dating back as long as car existed.

About the only thing you can try is check or have the dealer flash with the latest version for that VIN's ECU

The next thing would be a complete comprehensive engine health evaluation

Comp[ression test
Cylinder leak down test
scoping the intake manifold and combustion chambers
Oscilloscope and look at coil and spark values
Do and EGT test
do a AFR data logging
Check and compare DATA logging on acceleration run measuring Turbo response time and total boost produced @ target RPM
Lastly check the type of fuel used, what brand and what octane.



Somewhere[b] you are going to find something that is not up to the high end of operating values.


Dealers will likely not want to do this service and will probably say it is not needed and or refer you to an independent service shop. If you do decide to go to the trouble find a service shop that has a DYNO which is actually an important tool to seeing results as well see what your baseline engine output is. Don't compare that number to what is advertised or claimed by Mazda because most all power numbers are not SAE Certified so Mazda like most all auto manufactures can claim any power number they want. If it is advertised SAE Certified that a power output number then you know absolutely is an actual number.