Strange AT acceleration behavior

Andi370Z

Hey guys,

first of all, sry for my english. im from germany and its really hard to explain what my problem is, but in my country noone can help me...

So as the title says i have a more or less big problem with my at transmission (I think)

best to see if i drive in manual mode
when i start accelerating from rolling in the 2. gear and shift up to the 3. gear the rpm raise from about ~2000 to ~3500 as they should - then drop down to ~2500 again with a second of staying in this position (all while still accelerating in the 3 gear) and then it goes up as nothing is wrong. same in the 4. gear and maybe in others too but its best to see in the 3.

i have a transmission oil cooler and the fluid was changed about 1 month ago. there was nothing strange in the old oil.
the car has ~90.000km

erm. and a stillen g3 intake and lightwight pulley, 200cell hjs cats, armytrix exhaust and finally an ECUtek tune. if its good to know.

hopefully any of you can help me,
thanks in advance
andi