Ok so I have a 05 chevy tahoe with the 5.3l in it. It has 197k miles and overall runs real good. I bought this truck about a year ago and it had 165k on it at that time and my oil pressure was about 10psi at idle and about 35-40psi on the highway. About 4 months ago it started dropping to 3-5psi at idle and 20-30psi on the highway. Well the 3-5psi was quite concerning. Every time I'd come to a stop at a light or stop sign it'd drop down and the warning bell would start going off. As soon as I started moving again the pressure would go back up and the bell would stop. Needless to say this was very frustrating. I started using heavier oil on my oil changes thinking it would help it and it would keep it from dropping below 5psi for about 2 weeks but would then thin out just enough and the bell would start going off again at every stop. I've watched alot of videos on this issue on the 5.3l and alot of ppl are saying it' the o-rng at the top of the oil pump pick up tube going bad and also alot of ppl say that it's a clogged screen in the tiny filter under the oil pressure sensor. 4 days ago I finally had the time to tear into it and try to fix this problem b4 I do real damage so I changed the o-rng and I put in a new oil pump for good measure and it did NOT change my oil pressure at all. Also I did check my pressure with a mechanical gauge and 3-5psi is accurate. Also there is no tiny screen filter under my oil pressure sensor. According to a ton of videos these 5.3's are supposed to have that filter. So idk if someone removed mine b4 I bought the truck. Regardless I still have bad oil pressure and myself and a few of my friends that are real mechanics are at a loss and are not sure how to fix this problem. Note- there is no engine noise, no knocking, valve chatter, etc. If u didn' look at the gauge at idle or hear the warning bell going off you'd never think anything was wrong. ANY advice would be greatly appreciated. Thanks in advance.