okay guys, here's the deal
I have a 1991 300SEL with 168000 miles. My question is what should the oil pressure on the gauge on the instrument cluster be when idling??? My oil level is okay. I have no leak and and the level holds. No black smoke, and the ngine runs and idles very smoothly. But after running on the highway or at high speed, my oil pressure reads close to zero when idling. Is this a problem?

Also, anyone who can give me instructions on how to change my fuel injectors would help. Thanks