Sensor sigal noise

Hi, new user here. I have a 1989 Porsche 944 Turbo and I have a weird issue that's been plaguing me for a long time. The car runs ok, but not perfectly. Most of the time it feels a little weak on part throttle, especially at lower rpm. Every now and then it temporarily "fixes" itself, and it feels like I've dropped a few hundred pounds of weight. It's just that bit more eager to go...really noticeable from around 2k rpm. But it usually goes back to it's old self again before long.

Anyway I've done a lot of things over the years, fixing vacuum leaks, replacing ignition components, having the injectors cleaned, testing sensors etc. - all stuff that needed to be done anyway since it's an old car. But I never found anything that improved this issue.

Lately I was playing around with an oscilloscope for an unrelated issue, and I noticed that I sometimes have a lot of weird noise on some of the sensor signals (this car has Bosch Motronic fuel injection). I've attached some screenshots - the red trace is the throttle position sensor. You can see these really weird pulses of high frequency noise once per revolution. The blue trace is an ignition trigger signal around 90 degs BTDC. So it's clear that the noise starts somewhere close to TDC, but only every second trigger pulse.

Sometimes this noise is not there, and sometimes I pick it up on other sensors. In the zoomed out screenshot, you can see a trace of it in the green signal (which is the airflow meter).

So I'm wondering, what could be the cause of this noise? It's clearly happening once per revolution, and it's much worse under load. Also, the length of the pulses increases with load - if you look at the zoomed in screenshots, you can see one of them has much longer pulses.

If it was coming from the ignition system, then it should be twice per revolution, unless it's just one cylinder, in which case it would be once every 2 revs, right? I honestly can't think of anything that happens once per rev that would cause interference like this. I should add that the sensor itself is definitely fine and there's no noise on it when the engine is not running.

Another thought I had is that my scope probe is somehow picking up noise that's not really in the signal at all. Is that possible? I attached my probe grounds to the ECU ground for this. You can see a small trace of the same noise pulses in the blue trace though.

I don't even know if this has anything to do with the issue I described. But since I sometimes see noise like this on the airflow sensor, I think it could be related. Anyway I think I should investigate it since it doesn't look right. Any suggestions on where I should look next?

Thanks!

Hello injb
Did you resolve this issue or find anyhthing causing it ?
I have a 951 that has an intermittent misfire issue which is proving to be quite elusive.
I am waiting for my oscope so hopefully that will provide some answers but i have doubts...