Hesitation upon Hard acceleration
 

91 s10 blazer 4.3 4wd.

new fuel pump
fuel filter
air filter
plugs (ac delco,i have not replaced the cap & rotor yet)
tps
iac
egr cleaned
most vacuum lines replaced.


I have a 02 sensor code showing only when im cruising a steady speed for a period of time. The cat was bad so i cut it off and until Friday im running open pipe right after the sensor. Is it maybe that that's causing the sensor code to pop up? When I floor it. the motor jumps up to 3500 or so as normal but the motor starts hesitating and having no power. If i gradually ease into it the blazer is fine.

I just got the blazer with a bad pump and Ive been driving it for 2 days.