Help, engine won't rev over 2k

[Zsolt]

I also posted this on the V8 list, but maybe I can get some more opinions.

I am hoping I can get some insights why my engine wouldn't rev over 2000
RPM.

It's a 90 V8, has a new idle switch, speed sensor and breather hoses. It
starts well, and idles fine cold or warm. If I just gently touch the gas
  it would accelerate and shift up fine too, as long as it doesn't go
over 2000 RPM. Around 2000, however it starts bucking, and looses all
power. Ones it's below 2000, and again I just gently touch the gas it
runs fine, but every ones in a while it "chokes" for a second, then
keeps running ok.

The code indicates speed sensor, although it has been replaced. My
mechanic thinks it may have a couple of flat spots on the flywheel,
although it doesn't sound like it when I'm starting it.

Any ideas would be appreciated. Any BTDT?

Thanks in advance,

   Zsolt
   '90 V8
   '88 5ktq