Hey guys i have an '89 s10 blazer with a 350. its giving the o2 sensor code but we replaced it and its still showing the same code! But here is the problem. when i first start it it runs perfect gets the right rev that it should. but when the motor gets to normal running temp. and i hit around 45mph it sounds like it goes into an even lower gear and it wont respond when i hit the gas unless i have the accelorator pushed about halfway down. then it will rev back up and speed up.. but until the gas is pushed about halfway down it wont even rev up at all! any help????