What's Wrong With My Car?
 

I have an 07 997TT with GT3 TB, IPD plenum, Tubi Exhaust and EVOMS Tune.

In 3rd and 4th gear WOT after about 4k RPM the car feels like the rate of acceleration drops drastically. It feels like it's hit a flat wall. Then when I hit 7k RPM the car pulls hard for the last but but until I shift and then the same repeat scenario with 4th gear.
I just changed the plugs and checked the FPR for disconnected hose.

These occurrences happen no matter the temp outside from mid afternoon highs to late evening lows and I have also filled up from many different gas stations thinking fuel may be the problem.

What could be the possible issues so I know where to start the diagnosis.

Thank You

Post logs on datazap.me and link here, without logs you are only get guesses from ppl anyways...

I second the recommendation for some logs. It sounds like timing pull, as that's the meat of the torque curve where that tends to occur. The log should show it clearly, and we can assist in diagnosing why it's happening if that is the case.

If you are running the factory clutch I would throw that into the mix. With the mods you listed you more than likely will overtax the stock hardware and it will slip.

I will get some data logs done and report back.

The clutch isn't slipping - thankfully.