Mazda Forum - Mazda Enthusiast Forums - New to the mazda world

Hey!! Congrats on the new-to-you Mazda, and welcome to the site too.

At 54k you won't need plugs (NGK TR6IX, 3689 @ 75-100K,) but you may have another minor problem.
If you are experiencing rough idle, keep in mind that these are not the smoothest, most civilized engines to begin with. But I do have a few suggestions to look or lookout for.
Obviously you bought the car used, so you may want to:
1) Make sure all the engine (motor) mounts are in good condition and have not been replaced w/aftermarket "performance" style mounts. These are common upgrades and are a weak point in the original design, but guaranteed to increase engine roughness felt in the cabin.
2) Clean the MAF sensor. There has been much writtien about this, plus instructions on any can of cleaner for a safe way to clean these delicate devices.
3) Another thing I had trouble with a few yrs back is the check valve for the closed fuel evaporative system. It's a small device located at the front of the engine compartment, nearly dead center. It has a short hose attached to it that allows fuel vapor back into the intake manifold. If it sticks it can cause all kinds of strange symptoms. To unstick it, simply take a screwdriver and tap/rap the valve with its handle a few times.
4) And of course check the usual, air filter, PCV, and EGR valves and vacuum hoses.
I have not experienced any issues w/my EGR, but some have, and it is a part that will eventually need to be changed on all vehicles. They can get clogged with carbon and not work correctly. They can also experience vacuum leaks.

My car is an '04 with only 65k on the clock now, but I have had few issues with it in that time.

I wish you Good Luck with yours.