2.5 to 3.0 Exhaust

I guess back pressure is not the right word to use. With the larger 3 inch pipe compared to the 2.5 pipe you are going to lose some savaging, you will have more exhaust turbulence happening at low rpms which slows down the exhaust flow, which will effect the low end torque. At higher rpms there is no problem with the exhaust flow and the 3 inch exhaust will work better if your motor is tuned properly. Smaller diameter pipes will usually produce better low- to mid-rpm torque. Larger diameter pipes usually produce more mid- to high-rpm torque."