I just bought a 2006 F350 crew cab with the 6.0 power stroke. It has 4 inch exhaust, afe cold air intake. Has the 3 gauge pillar inserts with pyro, trans, temp, boost. Leveling kit with 35 inch tires. What are some good upgrades to get little better milage and performance? What are some of the signs I need to look for with common issues with these motors.