93 4.3 with rattle in engine

I have a 93 pickup with the 4.3 and 180,000 miles on it. When driving, I hear a rattle that gets worse under load and at higher engine speeds. It's a light rattle that almost sounds like pocket change. I checked it out with my handy dandy Sears stethoscope and heard the same rattle under the passenger side valve cover at idle. The truck is running fine. I've put about 40,000 miles on it in 3 years. It blows smoke briefly at startup, and has done so since I got it. It hasn't gotten worse. I had a code 32 fiasco until recently and replaced the following:

plugs
wires
cap
rotor
coil
egr valve
egr solenoid
fuel filter
fuel pump (which solved the problem)

Any help would be appreciated.

pull PCV valve out and plug end with thumb to see if noise goes away. New PCV valve is only $3.