2012 Mazda 3 GX MT5
Hey Thanks !A lot more likely than piston slap. Especially after 150k miles. Very likely there is a little bit of buildup there and the system in general. Not a lot, but just enough that it runs a little different than you remember it running. The trick is, that cleaning off the top end injectors, valves etc. works better over several tanks hence the larger lucas additive bottle works very well for this. After 3-4 tanks the car will run a lot closer to what it did when new.
Ive been using the Liqui Moly injector and fuel system cleaner Jectron Fuel Injection Cleaner
I have used lucas before maybe use it in between liqui moly stuff