I have this second hand civic 1998 ek3 with d15z6. I was adjusting the valves and changing timing belt. i realised that parts didnt look stock d15z6?

There was p2j-6 stamp on the head, p28 code on upper timing belt cover, p2j-00 code on the intake manifold, pm3B on the cam gear.

So previous owner made mini me swap? Are those from y8, right?
Car was running really fine for 1,5l but recently it has lost some power. Vtec also kicked in strong at about 5000 rpm, but d15z6 only has eco-vtec. Mini me would explain many things. Can someone confirm my theory?
i´m little confused