Thanks for the quick reply - it could be the VTCS solenoid valve. or the solenoid itself. My logic says if either are faulty, then the CAS (CPS) sensor would - as you suspect, regulate the output with a limit on revs.
P1512 would indicate a VTCS fault, with codes P1569 indicating low input and P1570 a high input. Sorry - no idea what this means, electrical or oil pressure? (I don’t see how you measure oil pressure?) I don’t have a Mk2.5 workshop manual, only a Mk2, so cannot say what it applies to.
That is, if my interpretation of the drawings is correct, VTCS I assume means Valve train control solenoid.
(Both are on the back end of the camshaft L/H side if you stand at the car front.)
According to my Mk 2 manual, the CAS is at the back of the camshaft, but when I mentioned this several years ago, I was told on the Mk2.5 it’s on the front. Not had a problem - thank God, so never had to search for it!
However, it seems logical if Mazda stuck the VVT valve and solenoid in the former Mk 2 position, then they would have to move the CAS to the other end of the camshaft. However, my Mk2.5 electrical manual shows the connector for the CAS in the centre loom at the rear of the engine - go figure.