The other item you listed is a slight increase of air temp caused by compression. That's just a fly on the puckey.

I still maintain that the air charge temperature will increase for the same reason that the EGR will lower temps. Of course, I am just going by what I've read and what makes sense to me. I wish I could get some concrete numbers. I'm okay with being wrong, but in this instance I will err on the side of caution.

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1982 300CD Petrol/Black Leather

I also said that it increases the stress on the engine because it is having to compress more air from the higher boost levels (essentially increasing the compression ratio). This will likely lead to premature head gasket and lower end failure. A few members here have foolishly run 30 psi or so for extended periods (weeks or months) with no reported damage.

This weekend while driving the line to my pressure actuator on my VNT (acts similar to a wastegate) came off while driving (crummy vinyl hose). I heard the change in the turbo's sound, looked down at my boost gauge and saw that I was getting over 20 PSI of boost. I was on the freeway so I continued along to the next exit at freeway speeds. I did not notice an increase in EGTs or change in power (I do not have the overboost system installed in this car).

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine