01 blazer 4.3 auto. The truck hesitates and boggs down at 2000 rpm to 3000 rpm. If i stomp on it it takes off. Cold open loop runs great , closed loop is when it acts up. New map,mas,tps,wires,cap,rotor,plugs,fuel pump,spider,cleaned intake and tb. Fuel pressure and leak down checks good. No codes set. When the truck acts up the upper o2s read .04-.90 v. if i really give i the gas it holds at .800-.900v. is this normal or are the lazy? While at idle the numbers jump around like the truck is acting up.

all replacement parts are all ac delco