2004 double cab TRD intermittently cutting out when accelerating between 50 and 60 mph

Hi..I hope this is the right place for this. My wife's truck kicked a code for for the catalytic last week (P0420). We cleared the code and it has not come back. The truck for the most part runs fine, and I am not getting any smells from the cat...it doesn't seem to be lacking in power. The truck has 90,000 on it. my wife is the original owner and other than some slightly larger Toyo's on it, the truck is stock. When we are accelerating, only uphills around 50-60 mph have we noticed it, the truck almost seems like you are shutting the key off then back on rapidly. after a few moments, it seems to straighten out. It kicks NO codes. I am at a loss. Any insight would be great. If I wasn't already in the middle of a bunch of frame repairs on my own truck I would drop it off at a shop, but I'm feeling rather broke at the moment!! Thanks in advance. Scott