Can someone help please?

Truck runs fine until it warms up, then it
starts to sputter a little, jumps slightly
when in idol and continues to sputter
when i push on the gas. My amps start
jumping back and forth, more toward
the low side. Almost feels like its going
to die. My parking lights started to
blink even though lights are off. I took
to a mechanic and they cant find
anything wrong. Thats crazy,  it
continued to do it after i picked it up. I
replaced the battery,  checked
alternator,  got a tune up. But it just
continues... any suggestions??