1989 740tic, 118,000 miles.

Had to move the car to another part of the "estate" to do some flower gardening near the driveway. Let the car idle so as to give the engine some runtime, as I do not yet have the car licensed.

After about 15 minutes, I revved the engine until it achieved redline at 6000 RPM. This was to "exercise" the turbo some. The turbo guage slowly rose from "8 o'clock" to just into the yellow band at the highest RPM range.

Immediately it began sputtering, as if it has a bad spark plug. I could stimulate this symptom on each try.

I let the turbo idle dowe then shut off the engine because I was done with it.

While moving the car later, I gave it more of this high rev, and noticed a puff of blue smoke out the tailpipe.

It never had done that before.

Did I uncover some latent engine problem here with the sputtering and blue smoke, or did briefly redlining it merely open the wastegate and dump some oil into the intake somehow?

Is this sputtering normal at the redline?