Chevy Vortec 5.7 MAF readings on scope

Greetings,
I’m troubleshooting random misfires on a rebuilt 5.7 that’s now a 383 stroker from 1998. The engine misfires at cold idle, but only the computer notices. Under throttle, warm or cold, the misfires almost disappear. Once hot, the misfires in Park are very noticeable! But, in gear, generally only show up on decel. I believe I have an electrical or computer problem.

I’ve done more troubleshooting than I should have. It would have been more efficient to just start-over. That said, I’m now venturing into scoping, and I’m a rookie.

 

I know it’s a cheap scope, but attached is a picture of my MAF sensor at idle. I’ll have to capture a throttle snap tomorrow, but a few things seemed odd to me that I’d love some help with interpreting.

- the negative voltage readings
- the frequency slope since it’s sitting at idle,
shouldn’t it be stable?

The scope is connected to MAF signal yellow wire and battery ground.

Any observations/directions/thoughts/tests to run are much appreciated. Am I using the scope wrong?

Thanks in advance!