hi PeeVee

i have the same problem like you .

i rebuild 2 engines,with all new bearing, (ACL race bearing, first time taht i use its) and higt pressure oil pump

conrod are new
crank is very good

and low oil pressure,
1 engine 1.8b at 900rpm
2 engine 1.4b at 900 rmp

at 4000 rmp, 3.6b

on my sierra RS i have 2.2 at 900 rpm and 5b at 2500 rpm

do you have any information or solution ?

many thanks