Why does 1989 Chevy truck 5.7 engine idles rough and will not start right up and hold steady idle?

because it is efi. which was a horrible mix of carburation and electric fuel injection i have the exact same truck right now and I am replaceing the efi with a holley carb. look into switching or replaces your efi. i would advize to getting rid of it since they are notorius for problems