Misfires

This car has done this for 3years. And that is how long I have had this car it is a 2.0 you start it cold or hot it dont matter it misfires. You take off in first and it about dies you have to floor it and dump the cluch to start out then it will misfire tell you get to 4thousnd RPM then its as if a rocket has been set off and will out run any thig on the road as long as you are above 4,000RPM. I have done every thing plugs, roter, cap, wires, fuel pump, filter, vacume lines, air box, intake gasket, cleaned and checked injectors, nothing has helped. Took to a shop last week they said they fixed it. Dont no what planet they came from but they did not do any thing but charge me $500.00 PS the plugs, cap, roter and wires have been changed more then once!