I respectfully disagree with Jeff. If you are contemplating mildly modifying your truck, of those three, pyro-tranny temp- boost, hands down, the least important is boost. If you had to pick one to do without, boost would be the on. When towing, exhaust gas temps are critically important, as is the temperature of your tranny. You will know if you are low on boost. That is not to say boost gauge isn't important, but it is the least important of those 3 in my humble opinion.