01 dodge ram w/ 360 5.9L burning out tps?

Ive changed my throttle position sensor in my truck almost 4 times in the last 8 months. Ive tried buying them from different stores/ different brands. They work great at first then usually a rainy day it starts sticking at 1200 rpm's at stop signs. Ive had the wires checked that plug into the TPS and nothing wrong there. Im not sure why this is happening but im looking for a little help. Has anyone else had these problems? Im more of a farm mechanic than a auto mechanic so is there something im overlooking. Like maybe it isn't the TPS? Im just guessing it is cause a new one fixes it. Also Ive had a few times where it looses power and backfires. Is this related. Anyone who knows alot about these trucks id really like to chat with you maybe learn a little!!