I know theres probably hundreds of threads just like this, but i was curious as to if i will need a tune for my bike with the slip on. If i remove the pre-muffler and the muffler will it cause a backpressure change?
As long as the catalytic converter is still in the header, no. 'Have to' and 'should' are different statements. All motorcycles are already lean due to the EPA. Lean bikes run hotter than rich ones do. More power can be had by increasing fuel to what would be considered ideal for power vs. ideal for emissions.