Help!

I still got the exhaust popping on acceleration and it's BAD but here's the rub;
For a while I thought the problem was gone but it came back with a vengeance but the weird thing is. it went away again. The engine seems like it has power, yesterday I smoked a rude driver that wouldn't let me change lanes on the freeway. They were going 70.
Today I drove 20 miles and it did it's popping again BAD. I felt a lurch in the engine when it did it too. I drove back and it did it until I reached my hometown then it settled down. Now it's gone again.
What's throwing me off is that it's so intermittent. EVERY check has be done to ignition, timing, carb, manifolds. It starts fine, revs fine.
The only thing that's constant is that every time I take this particular trip it starts this popping in the same area and quits in the same area coming back. I'm getting to think the car is demon possessed now. It doesn't want to take this peculiar trip.