Help with '99 L31 ECM Tune

[CJstein]

Good morning,
I'm as noob as they come, to tuning, so I apologize ahead of time, if this isn't the right Forum for my issue. I rebuilt a 5.7 Vortec from a '99 Yukon and dropped it in my CJ7. The engine came from a junk yard with only 100,000 miles, but didn't come with the ECM. I ordered a cann tuned Red/Blue/White/Black ECM and it starts, but Cylinder 8 is constantly misfiring, even though i have spark, fuel, and compression. The cam, pistons, lifters, rods, and springs are OEM. I tried reading the ECM with VCM editor, but because it's a cann tune, it's locked. However, while it was running, I played around with the VCM Scanner's Special Functions and adjusted the Absolute Timing to 0.5 and the misfiring went away Initial Run 5.11.23.hpl. Since I can't edit the cann tune, I found another ECM at a junk yard, for the same engine, but it has its own issue in that anytime the RPMs reach 1500, they automatically drop down to idle, even with the gas pedal floored and I don't know why. Is there a way to order a stock build for a '99 yukon to overwrite the junk yard ECM I have? If not, can anyone recommend a fix?

[gtstorey]

Need to post in the gen3 gm v8 section.

[CJstein]

Thanks. Done