VZ SV6 4th/5th gear no acceleration weird revs

[2agle_2ye]

Hey guys,
So with my auto SV6 I have noticed that if I am just cruising in 5th or 4th gear at like 1000-2000rpm my car has some serious problem accelerating in those gears. It's easier to notice if I basically floor it in those situations the revs will go up like 500rpm drop back down and then pick up again and eventually my car would accelerate fine....

It is more noticeable whilst in Active select mode using the paddle shifters as it tends to downshift more in auto mode and I am aware your'e not supposed to gain crazy speed in those gears but this is definitely not supposed to be doing this.

Another thing I have noticed is when I change from like 1st-2nd or 2nd-3rd at 3500rpm the revs will drop down into 2500-3000rpm in the next gear and then lose like another 500 rpm and then fluctuate back up and it sounds awful.

Lastly I think If I fully stop and accelerate from 0 the rpm from 1000-3500 seems slower and after that it picks up almost like turbo lag lol but this may just be superstition im going to record it on video tommorow.

So far I have had all this done:
Coilpacks
Plugs
MAF clean
Air Filter Changed
exhaust checked
Torque Converter Replaced
fuel filter changed
oil changed + filter

Any help would be greatly appreciated coz I am running out of ideas I don't know if it could be vacuum hoses? or maybe a blocked catalytic converter? or throttle body, intake manifold or a sensor i'm not too sure :/

 

[shueardm]

Throttle position sensor?

 

[2agle_2ye]

ok so could it be throttle position sensor even if you use cruise control? because I tried that and it still did it :/ Also if I drop a gear and gain revs it doesn't tend to do it either but it still will if im going a certain speed...