U7186 Predator tuner keeps bringing up REP mode

[chevrolade]

hello.i have a 2008 Silverado Duramax 3500HD Dually ,i just bought the u7186 Diablosport Predator tuner...its bone stock btw....just for kicks we tried it on the 3rd setting and well it woke it up very nicely but sadly it keeps putting it into reduced engine power mode everytime i try to even get on the pedal,and i dont race or anything i pull a gooseneck trailer everyday!....So i backed it out and set it on the lowest tune ans still seeing REP mode...also its saying on dash (change diesel filter) but a buddy of mine says his DMax always says that as well something about fuel rail pressure,idk.....id like to know whats needed or what do i got to do for it not to go in REP mode,it sucks having to stop every ten minutes to clear that out and drive again till it comes on again!
btw i have a SB cold air and MBRP full 5'' exhaust on the way.then my buddy tell me i wont be able to install the exhaust with my predator due to the dpf?

any tips or help would be greatly appreciated

[mikel]

all the answers are there...

if the truck is telling you it needs a new fuel filter, it NEEDs a new filter