So everyone that has an offroad x or h pipe has there check engine light on?
Unless you have obd 1. Which only goes up to early 95 models. Yes your check engine light will come on. If you are doing this work yourself. Make sure you know what you will have to do to take off the cats. My personal thought for you would to go to a muffler shop and flatbed your truck their tell them it's a race car (or your making it one) take the plates off so it looks so. Less restrictive cats might be better.(IMO)