97 1500 New trans, please help

HI EVERYONE, JUST PICKED UP THE TRUCK TODAY WITH A NEW TRANS fixed..truck works awesome Except......a few times on the drive home, truck lost all power, made some backfiring noises, shuddering and then when i put it in neutral it smoothed out. Almost feels like fuel starvation. anyway i know the tranny shop should be responsible but he's a buddy of mine and you know the rest, says the tranny is not the problem..FEELS LIKE AN ELECTRICAL PROBLEM ONLY INTERMITTENT..Could you damage a plugin/sensor or something during removal/instal of trans?

THANKS