The trucks have memory capability in the computers . (At least fords do ,Not sure about others ,) They adjust to your way driving . I'm not realy sure why you would need this . My opinion is step on it if you want more and go easy if you don't ! But anyway , The computer compensates to your driving needs and forms a patern to suposedly make things more to your liking . When you add a chip , (The right chip )

It mostly takes over the whole system and bypasses most of the computer . The more simple and cheaper chips just add info to your computer instead . This added info is proccessed and is also recalibrated by the computer . So it's like like 2 different computers fighting each other and in the end , the truck wins . When you use a programmer , You are only adding info with nothing to back it up (NO CHIP) . The factory computer will eat away at this over time and things will change . Also if you change chips as I do all the time , to try different programs , or different makers, You must delete this memory from the trucks computer . Because if you had a chip in and take it out , it will still have some of the old one in the memory .
I just did this with mine . 2002 ford , tri power from western diesel . The full package makes up to 160 hp . I took it out and just put a 50 hp chip in it with out doing a memory delete.
DAM !! It had so much power I thought it was going to rip the tires off !!!

So it took what it knows about that 160 hp and added more from the 50 hp chip . That was a shock !! But I wanted to see if it was true ,and YES it was !
HAd another one were a guy had the superchips programmer installed in florida . His exhaust temps were 1500 + !!

With just the truck !! And very little horse power gain . ( Suposed to be 80hp) I took it out and put the 'WD' 75hp chip in . It had much better power and only 1150 degrees on exhaust . THEN ,, in only 2 weeks , It started feeling week ....... I did the computer memory delete on it and it got real strong like it should be and has been for some time now . So even the programer that I removed still had a little battle left in it for the chip . But it's strange that it had less power then more , like mine did . Of course I'm talking diesels here but the gas motors have this memory "problem" too. HOpe this help a little , JOE