2003 chevy trailblazer 4.2 NEED HELP

I have a 2003 trailblazer 4.2 inland v6 so i bought
the truck and it wasnt running so i put a new
battery on to figure it out. It starts great idles great
go to take off it only runs 15 to 20 and 1 to 2 rpms.
Ive changed the air temp sensor cleaned the trottle
body with the sensor inside it. I even got another
one no change so i changed the map sensor, the
variable timing soleind and plug nothing. So ive
checked the air filter its good the oil is hood added
treatment, new gas with treatment. If i resest the
ecu  it gets up in 2nd gear and about 30 mph. Also
the oil gague either starts at 80 when starting and
push the pedal but dives to 40. So i changed the
acceleration position sensor the pedal and the fuel
pump is getting fuel to tthe motor bc it always
starts and nevers just dies. Anyone got anymore i
ideas