Replaced my mass air flow but now

i had my car diagnosed and they said my mass air was bad and a o2 sensor was bad but could be acting up because the mass air . so the dealer wanted 550$ for that and I tried a local salvage yard and they had one for 75$ so I got it and put it in and now my check engine lite went off but now when driving down the road when ever I let off the gas and then stay on the pedal to go at a slow speed the car bucks in every gear it like a specific spot in the pedal it will do this does anyone have any ideas what to look for?

Uhhh.... I'm usually pretty good at figuring out what people are trying to get across, but you lost me. I've never heard of a MAS going bad unless you messed with it, or it was damaged somehow. Yeah, they're expensive and the boneyard is definitely the way to go to replace one. Perhaps you could elucidate more on your "bucking in every gear" problem. Is the whole car jerking? Just the gas pedal? Is it just a noise? Umm, if your O2 sensor is bad, it could cause an occasional over rich condition which might explain your problem. Or perhaps you should check your ignition system. Those'd definitely be my suggestions based on the information you've given.