No, it's definitely not the cats.
First: WHAT ENGINE does the truck have? While you're at it...
Fill in your signature so the truck's details show with every post. You can omit the model if it's the same as this forum's name and the century part of the model year. But put the 2-digit year, model (ONLY if different from the forum), engine size (ci for carb; L for EFI), transmission model, trim level, cab/bed configuration & wheelbase, transfer case model (if 4WD), gear ratio, tire size, miles (or KMs), single/dual fuel tanks, mods, maintenance, damage, repairs, etc. If you don't know all the truck's details, read this caption & follow the links in it:
DON'T POST THIS INFO because it will only appear in THAT post - not in EVERY post.
If there are any terms you don't understand, read this: Automotive Terms & Abbreviations
Uploading pics of your truck would also help. It's easy to embed them in your posts if you follow the instructions at this link: