Did you adjust the boost level? If not check out your wastegate. If I am reading your post correctly one reason for your seeming low EGTs is the fact that you are measuring Post Turbo.

From egauges.com: "Now, there is much discussion about the actual placement of the probe, and if you have read our instructions, you will find that we recommend the probe be placed into the down pipe. This is the easiest place to mount the probe and the least likely to allow the entrance of shavings from drilling and tapping into the turbo (also referred to Turbo Outlet Temp). However, you have to keep in mind that on the AVERAGE, the temps will be between 300 and 400 degrees cooler than what is actually being inputted to the turbo itself.

That is why many people choose the more extensive, more involved installation method of placing the probe into the exhaust manifold. This method will offer you a more “realistic” idea of the true turbo temp, and a more “real time” reading of the temps."

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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