While driving engine will not go above 3,000 RPMs?

My pickup started not going above 3,000 rpms when driving, this happen shortly after I was driving about 200 miles usually I stay in town, and popped up a check engine light... 3 days later check engine light is gone, but now I can’t go above 3,000 rpms, and if I try and WOT the engine back fires, but for some odd reason the engine will easily rev up to 5,000 rpms in park but not in neutral, transmission shifts smooth and engine runs smooth just as long as it’s under 3000 rpm! Pickup is a c1500 5.7 vortec.