I am seeing and feeling a choppy RPM signal and trying to diagnose. Combo is 5.3 single 7875 turbo, Terminator X DBW, t56 magnum. Junkyard d585 truck coils with brand new AC Delco 9748CC plug wires. NGK BR7EF plugs. KW7 170 amp alternator from 2020 Silverado powered by PWM signal generator set to constant 14V. Every wire in the car is brand new. Entire combo has less than 20 miles on it.

Verified both coil grounds on Holley harness to back of heads are tight. ECU power and ground are direct to battery terminals.
Two 4 gauge grounds- one from engine block to frame and another from same spot on block direct to battery. No other grounds.

Log that shows the RPM chop:


Not sure what to look at to diagnose. My first thought is the junkyard coils, but don't want to just throw parts at it.
Perhaps EMI noise from something?
Need more grounds?

Help please

 

Look at Crank and Cam signal integrity, I believe in the log they are diag 6 & 7. They count up errors on the Crank and Cam signals so it would be interesting to plot that over your Engine RPM plot and see if it even thinks there is a problem.

 

Thanks NicD, sorry for the delay in my response. I did look at diagram 6&7 and they were both flatlined at zero.