Any ideas

hello everyone! i have a problem with my 1998 lumina 3.1. at light throttle, highway speeds especially going up a hill it [skips or jerks]. more throttle and it goes away till cruising again. i got it recently someone put new egr,fuel filter,plugs,wires coil packs etc. runs great otherwise, but gas mileage is poor. sorry if this post is too long or been covered before. thanks everyone.

Many things can cause this. O2 sensor, tps bad, tcc bad, dirty injectors, a full scan should be done to look at misfire counts, fuel trim, and with a trans scanner gear ratio or slippage errors. In my case once it was a cracked plug.

thanx Maxwedge , very helpful.