Although some drivers have gotten amazing milage from the manual, the EPA estimates are proving the difference between the two transmissions with the average driver.
Good luck finding modifications for anything involving the CVT. Even the dealership are scared s***less of trying repair it, much less make modifications.
As far as whether the transmission could handle it, I don't honestly know. I do know that the transmission was NOT built for power, it was built for fuel efficiency. The CVT does not run at high RPM's unless you are accellerating or turn the overdrive off. And judging by the summary I just read on Wikipedia (turbocharger= more power) I would not suggest putting one in a CVT. Trying to run more power to the transmission would probably risk breaking the belt. Then you're out about $4k for a new CVT transmission.
Go with the manual.