Bucking issue when driving long distances

It used to be whenever it felt like it. It would buck driving around town, really bad on the highway, but some days it would do it and some days it wouldn't. It seems like temperature makes a difference. Now with it warming up I noticed it won't do it on short highway drives or driving around town. But if I drive long distances it begins to buck so bad I can hardly stand to be in the vehicle. Last time it started doing it, it would not stop. Drove for 2 hours on the highway with this issue. Got home and let it sit over night and next morning it drove fine. I have blocked off the egr, checked for intake leaks, checked for vacuum leaks, replaced the pick up coil, ignition mod, replace ignition coil as well as plugs and wires and I gapped the plugs myself.054. The fuel pump is new. I am a heavy duty mechanic myself but I can not find this issue. I do not think it is fuel delivery. I tested ecm and it checked out.