Low oil pressure 200 TQ

[Beatty, Robert]

I posted about this problem in the past, but now I can't find the post.
Anyhow, I have to try changing the oil, but I kind of doubt that this time
thats the problem because I'm certain I put in 10W40, which is the
recommended oil viscosity.

Huw posted a tidbit about checking the oil pressure relief valve  which
unless I'm totally off base, is the valve right behind the crank pulley that
has a wire coming off of it.  

I can see the exploded view of it in the manual, but I couldnt find anything
about testing it or about how its suppose to work.  Its been a while since I
had basic recip engine theory, but I believe this valve would regulate the
oil pressure to a certain extent, correct?  If so, how do I make sure its
working correctly?

Anything else I can check without dropping the oil pan to look at the pickup
tube or otherwise majorly dissasembling the motor?

Oh yea, the symptoms might help :P

Start the car up (89 200tq MC1), lifter on cyl 1 or 2 is EXTREMELY loud,
after a bit of idle (about a min) I can get it quiet by reving up to about
3k rpm.  Oil pressure stays good until the car is fully warmed up then it
drops significantly to where the 3bar alarm is going off at 3k rpm and it
looks like i have close to 0 oil pressure at idle.  I know its not the
sender, I changed that which did improve the response of the gauge and I
know the gauge isnt the problem either because the autocheck is triggering
as well.

Also this motor was almost fully rebuilt about 10-15k ago so its not
something like main bearings worn out or excessive high milage.

Thanks!

Rob