No get up and go! HELP!

HI all! New guy here. I bought a 89 mustang gt 5.0. Which sat for three years in a garage. put new fuel pump filter and throttle position sensor, and clean new fuel. I got it running and started to try to drive it. thats when the problem started. If I drive like my grandma and press down very gently on the gas peddle it will slowly pick up speed. If I am going any speed and drive it like I stole it grandma passes me. If I step on the gas peddle with more agression it starts to pop and acts like it is starving for fuel I think. It idels well so I am not sure where to go from here. Sometimes I can put the peddle to the floor and the tach drops from 3500 to 1000rpm. pops and trys to kick back in and pops some more. Does anybody have any IDEA??

Thanks

Rotoblade

I worked on an 86 that had been converted to EFI with same problem. Spoke w/ the owner for awhile and found out he had just changed intake gaskets. Checked the timing & it was 19 deg too fast. It did the exact same thing yours is doing. Might be worth looking into.

It could be so many things. One thing that comes to mind is the fuel filter - has it been changed? As already mentioned, timing might be a culprit. Are you throwing any codes??

Check your plug wires. Very comon to have them on the wrong cyl.and check timming.