Sounds like a fuel pump to me, car used to buck bad at high rpm, near redline...felt kinda like downshifting quickly w/out rev matching. I thought it was the fuel shutoff. It started doing it at lower and lower RPM's and finally I could not drive over 2000RPM, pump finally died on my 2 miles from my house. Have em' check that while the warranty is good...my guess is you'll find out for sure what it is within a few weeks.
