problem with??

hello guys..in the last time i am having a serious problem..in the morning the car is lit for up to 2-3 minutes warming up when it turns on gas it turns on the gasoline and starts running again .. when i am in motion gasoline with fixed throttle makes me slow and the speeds are falling, gas is not as tight as the speeds and speeds are not falling .. also it does not keep a steady idle it drops very low but it makes me here for a long time. was checked in 2 synergies and no harm came out and the diagnosis was both that they wanted a change in the Valve Tappet Hydraulic Lifter..so I wanted to source it in a third gear and told me that it was probably the injectors. what to do????