First of all i'm running a AFR tuned 5.0 XK that has been maintained well with
new injectors, spark plugs and valve cover gaskets in the past year.
Vehicle has muffler and resonator delete and X-pipe in place of where the resonator was.
Vehicle has been tuned to work with current exhaust system and is not an aggressive tune.

Off the line with light throttle the car is quick and drives well,
Off the line with 80% throttle or wide open the car bogs down and
then takes off really fast immediately after.

Where should I start? I am able to log data, what data should I be looking for?

Thank you in advance!

 

What tyres do you have and how much wear is on them? Is the traction control kicking in?

 

Pretty sticky tires stock size, lots of meat. Bridgestone RE003.
I've tried in track dsc also, same problem, not sure if it's a traction issue or not

 

Vacuum leak at big suck.

 

you tuned it now you get to fix it

start with trims

 

I think cee Jay is correct, so hard to find vacuum leaks that only show up under load

 

Update: replaced throttle body gasket and intake manifold gasket, fuel trims leveled out
and torque is back!

 

Glad to hear it, and thanks for the update.

So, a vacuum leak at big suck. Whoda thunk?

 

I wanted to add to this that my alternator was on its way out and was not supplying
enough current for sufficient spark, thus poor acceleration off the line as voltage
would drop until the alternator caught up.

Alternator along with the vacuum leaks created my problem.