Welcome to IRV2! When you get a chance fill out the information on your coach, year, make, model etc, it will help you here in the future.
I'm going to assume you have a C7, for this we have a plug and play module that adds up to 30% more HP and 250 ft lbs of torque. This module works as stated as we have installed several over the last few years. Bundle this with an AFE performance lifetime air filter and an Aeroturbine 5" muffler and you will have the performance and economy you are looking for.
Give us a call, we will be happy to add you to our growing list of satisfied customers.
Redlands Truck and RV