need help 88 sierra

[Revelation]

hello got a 88 gmc sierra 5.7l TBI been a bad luck vehicle for me so far but wanna make it right just bought it two weeks ago too so dont wanna lose money on investment i live in new orleans and all the mechanic shops are booked for weeks here so need some help to do it myself well here is the problem

sometimes its hard to start i have to hit the gas pedal sometimes while its cycyling to have it kick over and run and when it is running the idle is very bad sounds like it wants to die but only has a couple of times its getting worse each day need to get it fixed before it dies on me only vehicle i have and need it to get back and forth work etc

when i first got the truck it ran out of gas also appartnly 1/4 of tank is empty

so far i have replaced some things such as

replace the muffler and pipes because the muffler had a giant whole in it
replaced MAP sensor
replaced Knock Sensor
replaced Coil
plugs,wires,etc looks very new


any help would be appreciated on diagnosis