Sounds familiar..... .Little story from my own storybook:. .In 1991 I boarded an Tupolev 154M(Balkan-Air) to get from Nairobi to Sofia.. .Got the last seat on the right side of the A/C.. .Next to an emergency exit an with a good view of the engine.. .Clearly on the taxi-way (blue lights,just started my PPl training)the engines spooled up and we started to accellerate.. .I guess we where close to lift-off speed when the engines where put in thrust reverse and heavy braking followed.We made another turn and this time the lights where white.Relief....NOT.. .This time the engines only spooled up to a certain rpm,but not as high as previously on the taxiway.The sound was just all different.. .After quite a while of lights...lights...lights...lights..lights I expected them to abort T/O.Told my neighbour:something's wrong and I'm the 1st one outta here...as I reached for the handles on the exit.The plane rotated....hardly climbed...got a close-up look of the Nairobi citylights..... .Atfer a couple of minutes (still low rpm) we turned what felt like 180 deg.I prayed we where returning to the airport.Suddenly the engine accelerated to what sounded normal and we turned again,climbed out and headed to Sofia in the darkness of the night.I was so scared I went to sleep and didn't wake up till touch-down.Were supposed to take the same plane on to Brussels after refuelling.. .We were told the plane was found to be "broken" as they put it.Had to wait for a replacement which turned out to be a 737.. .Anyway...it happens...