2002 Chevy Silverado Intermittent miss

My chevy truck has a real bad miss occasionally after I have been driving a while. When the car is warm, it will miss when cruising around 55-60 mph (1500-1800 rpm). The first miss will be kind of mild, with increasing intensity. There is no check engine lights.

I just had a tune up (100000 miles)---new spark plugs/wires, new rotor in the dist cap, new fuel filter.

Any ideas? Thanks in advance!