tapping noise

[thclover1]

help i i have an 89 lx 5.0..i put an "e" cam in new melling
hy.roller lifters new sealed power lifters and newer stock
rocker arms,a 180 degree thermostat and advanced timing but not
to where it pings..the tapping starts after the car has warmed
up for about 5 minutes of driving it..but it only does it
between 2000 and 2500 rpms..sometimes it stops after it goes
over that into higher rpms sometimes it doesnt... also have mac
unequal shorty headers with offroad h pipe and did away with the
polution tube and air pump...i have tightned every exhaust bolt
with a heavy duty impact so i know those are tight ...and every
bolt is tightend to spect....i have no idea where this tapping
sound is comming from....i have had this motor torn town atleast
20 times trying to fix it...i am out of ideas...can someone
please help me...i am running royal purple 5w30 motor oil by the
way....oil prressure at idle is mostly at 50psi and driving is
at around 60 to 65 psi....and help would be appreciated...thanks
in advance...