main bearings

So I have 3.8l 231 V6 non turbo 87 regal, the engine has 187k+ on it. For engine oil pressure at 1600-2000 rpm’s it’s at around 20 psi on cruise. Idle is about 12 at 1000 rpms. But at stop lights when I’m in gear the pressure drops below 10 psi. I did the timing chain cover, I replaced the oil...