lild1991RS

lets see my 1991 RS 5.0L tbi had been sitting for three years. finally decided to get it back on the road because my other car had got repoed. it has been sitting because the clutch is too far gone but anyways. the engine will fire rev up to 2000 rpms then die. i can kinda keep it going by hitting the gas but will not rev over 3000. if i hold the gas it dies. it had a 1/4 tank of gas in it so i filled it up with gas, put some treatment in the tank then did a full tune up. pcv valve, air filter, fuel filter, oil change, spark plug/wires. and the engine will not stay running. can some one please help me through this process of getting my engine running right so i can focus on the clutch an getting it street ready?????????