318 magnum,is my oil pump failing?

i have a 1994 318 magnum motor in a 4x4 thats been giving me some odd readings.
i run regular 10-40 in it.
it will show around 40lbs pressure warmed up,
but can and will drop low enough to pop the oil light at times,
sometimes while Driving others when coasting to a stop.
this Doesnt happen All the time either which is why im a bit puzzled.

initially i thought i had bad bearings,but the pressure comes right back up to 40??
theres no noise at all/complaints from the engine itself.
i regularly wind this to around 4 grand/manual trans.

and,this week the plenum gasket went bad completely,
im sure its been bad for awhile but now im at barely driveable.
ive looked up the hughes kit and will be getting that shortly.

are these 2 events connected?
or do you think the oil pump is getting ready to quit..?
i thought if it was bad it would just stop working but ?
what is your opinions and maybe recommendations?