Ive been running the PHP tunes from Bill. On the Economy tune it spins the turbo very slowly, under 4psi all the time unless you really punch it. I noticed the sounds of the truck at idle is very different, a lot less of the hair dryer sound and when you accelerate its much deeper and less whistle.
On the highway it runs at 2 or 3 PSI boost untill a hill comes then only the boost goes up to 8 or 10. I was getting 18 steady for 700+ miles. Got over 550 miles on my tank and the low level never came on i just got nervous i wouldn't find a station at 2am.
I have more recently been running the 100Hp 200 Torque tune and it does the exact same thing. It only runs the Turbo at 1-4 psi unless you get over 2200 RPM then it lights up chits and gits.
At cruising speeds the turbo might be at 3PSI but it will spin it up and downshift really fast when the throttle is pressed.
Yes spinning the turbo Less gives better mileage when you are cruising. The faster the turbo runs the more fuel has to be fed in the engine.
Im still trying to get answers if this slower turbo PSI will causing carbonizing from PHP but i still get on her pretty often to make sure it all works.
I have been averaging 14.5 city up 2 from stock and 18 highway up 3 from stock