Warm-up regulator pressure on Audi 100, 1989

I have an 1989 Audi 500 (South African name for the Audi 100 with 5cyl 2.2 engine), . Recently, someone checked out the fuel injection
system. He said, the pressure of the warm-up regulator was about 0.5 bar too high (4.2 bar instead of 3.6 to 3.8, iirc). He said this would make the fuel mixture too lean, but a replacement regulator would cost a lot. He then adjusted CO at idle and just said that's the best he could do.
My questions:
- Is there any way that we could adjust the pressure on this warm-up regulator?
- How big is the effect of a too high pressure, and what are the consequences?
He said the the performance would be a bit lower than originally, but insisted that the fuel consumption should be lower as well, if anything. That doesn't sound right to me. With a 120 km/h general speed limit, I will not go full speed anyway. If I want to go at a certain speed (like 120 km/h), I would obviously press the acelorator to the required level to maintain this speed. I would assume that the fuel consumption is only optimum, when the mixture is optimum.
Any other effects, or should I not bother about it?
Thanks for your help,
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