Dropped car off for oil change today at 3000 miles. And drove a loaner g37 for the first time.

My car had an issue last week where I floored it from a stop and it moved forward a bit then down shifted (auto trans) and the Rome hung at 5000 but the car didn't accelerate, almost like the transmission was slipping majorly. It shifted to a higher gear rpm gauge went down to 4000 rpm, still didn't take off, so I let off the gas.

Then I gave it a little gas and it moved like normal. When I stopped I had an acrid smell almost like when you're burning the clutch on a manual.

Dealer said they can't reproduce the issue, could be a torque converter. But they wont try to fix until they can reproduce. So here I am and my g37s feels a hell of alot slower than the loaner g37 they gave me.

Any suggestions?