1990 Chevy 1500 5.7 headache

where do i start,
driving down the road 60 mph reduced speed to 50  when try to speed up
again nothing i could tell  something not right pulled over ,,
almost felt like was missing on a cylinder  or something
Long story short i have replaced EVERYTHING normally do not do this i
have had 2 mechanic look at it no useful info

new  fuel pump x2
fuel filter
map sensor
distributor  and everything that attaches to it
map sensor and coil was replaced within last year
egr valve replaced last 6 months
new TPS
new injectors
new fuel pump reg
timing chain and gears
and so on

my steering wheel is a little loose to pint i have lift gear shifter up a little to
shut it into  off potions

i had guy over looking at it while it was idling it died finally a symptom i
thought that is different when it died the  injector  kept spraying fuel i
unplugged them still prayed fuel , fuel pump would not shut off until i turn key
off notice this problem  over next few days run for 20 min then die  injectors
keep spraying  ,
replace injectors and oil pressure sensor


then stopped running all togetrher cant get it to start up , went to junk yard
got ECM replaced it reset it reset timing it fired right up runs great i thought it
fixxed the problem
i put it in reverse  drives great down ally put in drive to come back  it sputters
and is almost like someone is choking it i give gas want to die i let off gas
start running again
i am sure one of my new parts is junk but at end my leash with this thing just
trying to get it running fast enough to park it into a tree lol

i can start it up no problem let run  no issues rev up sounds fine  put in gear
give it gas it hesitates for a sec then wants to die soon let of gas it idles fine
again


any info would be help ful