I Hey folks

After searching around for the last couple nights I've come to the conclusion that it was time to get your guys opinion. I have an 04 silverado 5.3 4x4. I just got done changing out all the brake lines with genuine upgraded brake line with the plastic sheath. Since then I've been gettin a pulsating feeling as if the abs unit is coming on. I took it in a parking lot and experimented a lil bit. Under hard braking they work flawlessly. Then say coming to a slow stop is when the pulsating starts. I went one step further and slow stop and took my hands off the wheel and it pulled a big deal to the right. So I thought it was an easy fix and thought air bubble in the front driver side caliper. Well needless to say after bleeding the brakes a half dozen times it still continues. I'm assuming it has to do with the abs unit or sensors leading up to it? What do you guys think?

Thank you in advance
Trevor