Silverado 2008 RPM flactuating

[Silspark]

I have issue in the cruising in 4th gear from 1000-2000 RPM, in highway when the 4th gear is applies I feel RPM fluctuation between 1000-2000 so I have to increase the TPS to avoid this issue, I take log but is seems every thing fine but the timing is fluctuation due the g/c location

this issue is raised when we change the engine from 5.3 to 6.0 (LY6)

Silverado 5.3 2008

regards

[Jabbott]

If you look at your maf transfer function while scanning, what is the highlighted block doing? Is it moving rapidly or staying steady.

[Silspark]

The maf is fine and it looks smooth but I timing is bucking in that issue specially in low rpm in light load

[Jabbott]

I am sure the curve in the cal looks ok, but what is the highlighted cell doing during the surging. All of the air calculations originate with the MAF sensor so if if that cell is bouncing around it means that you have turbulance and it means the engine is seeing different air flow numbers but in reality it is not. It is moving the timing to whatever is in that cell with the corresponding cylair. What do your timing numbers look like in the cells next to each other when the car is surging. Is there a large spread in the timing numbers or small steps.