Thanks for the reply, G. Here's what's I understand and what's happening.
I'm glad to know about the slight fluctuations. I feel better about that now.
As for how the gage works, I understand that, and that's how my car has acted in the past. Pegs 3 upon start up, and drops once the car warms up, usually to just under 2, slightly higher in the cooler winter temps, and slightly warmer in the hot summer months. And always slightly higher when the oil is newest like right after an oil change.
As for how the car starts, it's always started best when cold, seldom taking more than one revolution to catch. When warm, it's seldom taken more than two, maybe sometimes three, revolutions to catch. And it's always idled at about 650 RPM. Depending on who's tach I use, I get a slight variation, but I assume that's due to calibration/manufacturer differences. But it's always close to that. The only time I get a different reading on the idle speed is either when the engine is cold (only a very slight increase) or when the A/C compressor is on. I've never had a problem with the car stalling either. Ever.
What's happening now is that even once the car is warm, and I mean in 90 degree plus ambient temps, the oil pressure never comes down. It always stays pegged at 3. No fluctuations at all on the needle. And that's even at the idle speed of 650 RPM. And the car is hard to start, always taking ten or more revolutions to start. And as noted, it's stalling regularly now. But once it's started, and as long as it's not stalling, it runs fine - very smoothly as always, but what seems to me to be slightly down on power.
Fuel pump is fine as far as I can tell. I'm familiar with the whirring sound your talking about, and it's not doing that. I replaced it two years ago as well. As for the OVP, I'll check that out. But if you're talking about the voltage protector that keeps the main computer from getting blown from voltage surges, I had that replaced by a Mercedes dealer a year ago. But again, I'll double check that.
The belt is a new one to me. I'll check that, as I put a new one on earlier this year. But if there's something else wrong, maybe I just haven't looked close enough to see it. I put a new compressor on a year ago, but recently converted the car to R-134, so maybe something happened there. But I normally turn the A/C off when I stop the car, and on only after it's started, so it would have to be the clutch if this the problem with the A/C. Also, I just had the alternator rebuilt a few months ago. And the water pump was replaced early last year.
The timing chain is a new idea to me as well. I've not replaced it, and it's been about 100K ago that I bought the car. I like this idea (you know what I mean - lol). Is the tensioner adjusted with oil pressure? Could this somehow tie the increased oil pressure and hard starting/stalling problem together?