155's can be tuned to make quite a bit of power from what I have gathered. I have a buddy with 180's in his truck and a II stage 1 turbo ( he needs a larger turbo ) and the 180's have a ton of fuel even pulled way back. What you really have to look at is what you want to do with the truck. If you still tow with the truck, I would just stick with the 155's and add more fuel to them if possible. If you are looking for a little more performance out of the 155's, try getting your FICM tuned. Eric can make the injectors stay "ON" longer (Pulse width) and get that last little bit of fuel out of your injectors. Hope this helps some.