Symptoms you have there sounds where just like mine.
Do you get to a point where you have your foot flat on the floor yet nothing is happening then all of a sudden the power comes back, then it will just go again?
It was fine one minute, but when I booted it in third and it stuttered up in the higher rev range a couple of times I knew my wallet was going to take a hammering.
Pretty much went straight to three cylinders after that, so phoned work and told them I was taking the day off and gently drove home.
On the bright side, it gave me a chance to give the car a good clean as the weather has been great today....and I watched a couple of old Top Gears on that new freeview channel called Dave. So alot better than being in the office