Of course the other reason for engine roughness might be the use of fine wire (iridium) spark plugs made by
Champion which have contained defective resistors for many years - see the thread I started here a few weeks ago
On your last para, this is why I have two oil temp gauges and two oil pressure gauges. Getting a 2nd oil temp gauge installed is usually trivial; mine was done via an extra probe on the EDM700. Getting a 2nd oil pressure gauge installed is usually not trivial (on a G-reg) but is unquestionably a Minor Alteration on an N-reg if done right, and
UMA make some nice compact (1.25") TSOd transducers and instruments for that.
I see proon has modified the rules under which it marks posts as edited. Previously one had ~ 1 minute to do edits; now it is zero.