Punch it and observe the RPM when the turbo kicks in. You may have a High Pressure turbo that does not kick in until ~3000 RPM.
The low pressure turbos are the ones that kick in at a lower RPM but peter out sooner.

The high pressure turbo lets you choose whichever side to pass them on up road a bit

Once it spools it’s good bye-M-W

Take a compression test and then look at your spark plugs while doing that

Remember the turbo won’t spool up on just rpms, it has to be loaded.

May I suggest replacing ATF? Hard acceleration happens with the torque converter not locked, so all of the engine torque is transferred through the ATF.

Idemitsu Type-TLS works well in this transmission.

The timing belt was changed by the previous owner about 40k miles ago, so I don't think that is the problem (unless the timing is off?). I thought about performing a tune-up, but since there are no miss-fires, and the previous owner changed the plugs when he replaced the belt, I think its likely so...

^^^ All excellent places to start. An inexpensive scan tool would possibly provide some answers as well. It may sound paranoid, but I keep a scan tool in every (running & insured) vehicle we own. They're like $10-15 and while they are extremely limited in their abilities with scanning P2's (&...

VIDA+DiCE can tell that.