Sluggish throttle response at 3K RPMS
 

So I have a 2014 Scion FRS . The engine blew and I engines swapped it with a 2013 engine . After all is said and done I’ve been doing some test driving and I receive a very sluggish throttle response at 3k RPMs . Not the usual issue for lack of hp. It’s more like I hit the gas’s ans the Rpms will rise past 3k with no gain in speed and drop back down to 3k and then go. It’s like a “sluggish” response . I’m going to take it to a shop to have it looked at but my thought is that maybe it has something to do with tuning or transmission .

Any thoughts ? Car has no other modifications other than 2013 engine swap(10k Miles) and a cam plate for that oil leak a few of us has dealt with .

AT or MT?
If auto.
Torque Converter?
Trans?

If manual.
Clutch slipping.

There is a very popular cat delete and oft tune to overcome the torque dip

Sounds like this probably isn't the torque dip given that OP had the car before the engine blew and it didn't have the described problem at that point. Also the torque dip is noticeable but it's not as bad as how it's described here.

It is a Manual transmission. Called shop and they said it could be a possible vacuum leak as well. But the clutch makes sense honestly.

Not talking about torque dip, tbh I think it is a result of clutch slipping maybe from misalignment. When I take it to the shop they’ll confirm.

Just took it to the shop, I pushed it and funny enough it wasn’t really happening. Seems like a inconsistent issue

After unplugging the battery for any reason, the computers have to re-learn how all the sensors are responding.
Takes about 200 miles to get a handle on that so it plays safe with computed signal levels til then.